You didn't mention it, so I will ask. Have you tried showing the Calendar tab by using the menu like I show in my screenshot?

If you don't see the menu bar, press the ALT or F10 key to show it.

Thank you. Yes I tried this, via menu and short cut. Nothing happens. It's so strange: everything (options. symbols or this menu) is there, but the calendar tab does not show up. I have no ideas what to try anymore. The TB version is a portable one. So I am now thinking of installing TB normal on the notebook and trying to somehow import the calendar if at all possible from the old data files.

I would very much appreciate any other ideas ...Thank you.

Thunderbird portable can only be updated properly by downloading and installing the new version over top of the old version: https://portableapps.com/support/thunderbird_portable#upgrading

Perhaps you let it update internally? If so, that may have caused this.

As for fixing this issue, I suggest backing up the Thunderbird Profile, then uninstall the portable app, making sure that the Profile is deleted also.

Install the portable app again, set up a new Profile, set up your e-mail, then import your mail, calendar events, and address books.

Thank you, I did always update the portable TB version internally (window saying there is an update, clicking ok .. download...and then restarting TB or postponing restart); this never caused problems but maybe this is the case now. Thank you very much for the suggestion, I'll try that out over the weekend.

I hope updating it properly will fix the problem, but I'm a pessimist, so expect that you will have to do the backup, uninstall, reinstall, and import.

Thank you for your suggestions. I'm sorry I'm not good at any of these computer works. I've "backuped" my TB by copying the whole folder to the notebook drive (portable works on an external drive to be able to take it to other computers). I've installed the downloaded new version of TB, after starting, I realized, that my recent version (folder) was named Thunderbird_3_Portable (don't know the reason anymore), so the new one was installed in parallel - no wonder nothing had changed. After closing everything, I renamed my recent version "ThunderbirdPortable" in order to have the new installation over the old one - that seemed to work. But as you expected, it did not help - now the calendar again does not show up anymore. (It did in the parallel new version, of course empty. I still thought I'll try the import - to have at least the calendar - following your linked instructions but failed already at the beginning: my TB-Data-profile-calendard-data folder only contains 3 .sqlite files and so does the backup folder of this folder: local.v19.sqlite and v20 and v20-1 all three .sqlite, no "ics" file. Also, these three are very old (2011/2013). So I copied the files from calendar-data to the new parallel TB version, but this did not help - the calendar data did now show up, just the empty calendar stayed.) So this installation on top of the old version did not help, I need to follow your long version, but I'm already failing at the first steps: - backing up the TB profile - is it ok to have the whole folder copied? (backing up via the back-up-option in portable apps stopped working) - uninstall TB - how? I've seen a page with several ways but already the first ones (via W7-start-.... I also would not expect this to work for something portable) etc. did not work, I could not find any option in the portable apps menu; just deleting the whole folder (ThunderbirdPortable on my external drive) would be ok? this would make sure the profile is deleted (it should not be on the computer itself because of "portable"...) - installation should be ok, I will need help with setting up all email accounts again but have something to aks for this as soon as I get there - importing calendar events without that ics file? I'm really sorry I'm getting stuck at the probably most simple things. I really appreciate your help a lot.

my TB-Data-profile-calendard-data folder only contains 3 .sqlite files and so does the backup folder of this folder: local.v19.sqlite and v20 and v20-1 all three .sqlite, no "ics" file.

... backing up the TB profile - is it ok to have the whole folder copied?

uninstall TB - how?

If you are using some other Portable Apps platform, then you need to figure out how to uninstall an app in that platform. If you don't, then deleting the ThunderbirdPortable folder will confuse the platform.

Once you have uninstalled it via the platform, then go and delete the ThunderbirdPortable folder if it still exists.

Then install the portable app again, set up all your accounts, then import your stuff from the backup of the old profile

If you need help setting up your e-mail accounts again, then tell me what the part of the e-mail address is after the @ symbol.

Thank you! After a first shock about the lost calendar data I now at least could recover some of them from an idea I had from your suggestions: I had saved all portable data on the notebook while travelling a month ago, everything was working then and I looked for those ics files: none. It actually looks the same as now: the calendar-data folder unter TB has cache.sqlite, deleted.sqlite and local.sqlite (when closed, when TB is opened, there are a few more shown) and the backup folder there has the same very old 3 sqlite files mentioned above, I don't see any ics files, although I actually do have same very old ics files from a time when I apparently exported the calendar so in general I can see ics files.

I now used the opportunity and exported all my calendars (from a month ago status, but better then none, some take very long resulting in a 4MB file), so at least I have now something to import once I'm at that step. But isn't that still strange that I don't have these files in a working 1-month-old thunderbird version? I'm not sure it makes a difference that I have everything encrypted via TrueCrypt on my external drive. (And I admit that the email folders are huge, TB zipped is almost 4GB.)

I do use the PortableApps.com (grey circle with an arrow, I start if from the windows menu bar, it shows this name too when opened/started, but clicking right mouse on the TB line does not do anything, hovering shows the location of the thunderbird, left mouse start the TB app; I have a few more portable apps like mozilla, gimp, notepad, open office stuff.. none of them reacts to right mouse click for uninstalling, but right, yes, I should uninstall it somehow via this program).

I unfortunately have a few other deadlines but the calendar is very important to me. I feel a bit better now having saved at least the older part of it. Would it be an idea to take my old version and replacing the current one for the moment (it has at least a working calendar to put in new appointments that I'm keeping on paper right now!) - I would loose part of my email stuff, particularly the sent ones and those already sorted into folders.. while trying to fix the whole problem during the next days? Really strange about the ics files... Thank you so much.

My bad. According to Files and folders in the profile - Thunderbird, the file "local.sqlite" is "Internal calendar data (in SQLite format) if you use the Lightning extension."

I've long since backed up my calendars to .ics files, then told Thunderbird to use those .ics files instead of that "internal calendar data" file. It is easier to reinstate .ics files than "local.sqlite".

If right-clicking on Apps in the PortableApps.com Launcher doesn't work, then perhaps the PortableApps.com Platform needs to be updated, reinstalled or something. I don't have much experience with it, having just experimented with it a couple of months ago, then since then not have any actual need for it.

Thank you! My portable apps was indeed extremely old and updating it took some time but now shows "uninstall" options. Great, there is then some hope for the calendar as well when I get to the uninstalling-installing of TB process.

Just to let you know: I've know installed the new TB, copied the old profile into it except for the calendar data (with those, again the calendar tabs were not visible) - apparently my sqlite calendar data base was broken, so I could only reuse the 1-month-old backup. Now everything is running so far with the current email status except the loss of 1 month of calendar work. My plan would be now to export all calendars at least weekly or alternatively shift to remote calendars like those from google integrated into TB lightning. It seems like working with them offline works ok as well (on journeys without internet). Thank you again for your support!

I recommend doing what I have done: 1. Export your calendars to .ics files. Save them in the calendar-data folder. 2. Delete the calendars from Thunderbird. 3. In calendar window/tab, Menu: File: Open: Calendar File. Choose one of the .ics files. Do this for each of your calendars.

Now, those .ics files will be used to load and save the calendar data instead of Thunderbird's "local.sqlite" file. These .ics files will be easier to reinstate later for recovery, or for importing into other calendar programs.