Does the shortcut Ctrl+N work? Does the same thing happen in safe/troubleshoot mode (hold Shift when launching TB)? The button works here in 138/W11.

Thank you. No none of those solve it. I checked both boxes for "extras and to reset something". A trial Malware bytes was about to end so I uninstalled that, but still no. I just bought this computer and have installed nothing that wasn't on old computer. Any more suggestions?

Is there anything unusual about your setup, such as you are running 138 on a profile that was used in a previous version, or the current profile is not in the default location? Many users have the New Message button hidden, but I have never heard of it not working. Is this the version from the MS Store?

https://thunderbird.topicbox.com/groups/beta/Tb0176abd7fa7617a

I did copy over the profile from previous computer. I found the instructions to that that several places. I also copied the profile.ini on the advice of a store geek when just the profile didn't work. We had tons of email addies and saved emails I didn't want to lose. Everything appeared in the new Thunderbird as in the old computer. I downloaded from the Mozilla site. Thank you for your continued suggestions.

Although the procedure for copying profiles from one setup to a new one is supposed to work in principle, in practice it often creates problems like the one you reported. Trying to fix it usually takes much more time and effort than building a new profile. Which is why I always create new profiles for each annual release or new beta channel. This shouldn't be necessary when moving forward from the new monthly releases, 137, 138,..., but it's recommended for moving between, e.g., 128 ESR and 137 or 138.

First step is to create a new profile in 138 from Help/Troubleshooting Info, about:profiles, add an IMAP account, and see if it works properly. The current profile is unaffected. If the new profile is working, local mail, address books and other data can be transferred from the old profile to the new. It might take a while the first time, but it's a valuable skill to acquire for future situations.

Thank you. I will try that when I have time. You have been very helpful and I appreciate it.