Try to set an allow exception for addons.mozilla.org and open the site in a tab.

You can inspect and manage permissions for the domain in the currently selected tab via these steps:

• Click the "Site Identity Button" (globe/padlock) on the location/address bar
• Click "More Information" to open "Tools > Page Info" with the Security tab selected
• Go to the Permissions tab (Tools > Page Info > Permissions) to inspect and modify permissions for the domain in the currently selected tab

Corel, youre going to think this is very strange. I just realized something.

Left clicking on that button does nothing.

Right clicking and selecting open in new tab brings up not the theme, but an addon named Personas Plus. I uploaded a screen shot (http://paulrittman.com/addons.png). Not sure what is wrong here.

Anyways, the permissions were set to Allow. I disabled that, and set the permission to Default, but the problem persisted.

http://paulrittman.com/addons.png is the link.

Darn Im not used to not being able to edit a post.

OK, when you look at my screenshot, you can see in the bottom left corner, the link that I see when my cursor hovers over the Add to Firefox button.

Do you at least see the lightweight theme getting loaded if you hover a theme on the Add-ons site?

• https://addons.mozilla.org/en-US/firefox/themes/

Note that previewing only works if the site is whitelisted via an allow exception.

You can check for issues caused by an extension that isn't working properly.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

No, hovering over that link doesnt let me preview the theme.

I did this also with addons disabled, and the same problem persisted.

I will try this with a new profile--I can only assume that this is a problem not with FDE, but with my configuration, since it doesnt appear that anyone else has this problem.

Oh well.... creating a new profile did it. I can now install new themes in FDE.

OK, but this still begs the question. I can simply use this new profile. I only need to copy over bookmarks, history, passwords. I know what to copy over.

But Im puzzled as to why I couldnt do this, before. I guess I can always just load up on a lot of themes now, so in case this problem reappears, I can still change themes (with the old profile, I was still able to change themes if I had already installed them). But still, Im wondering why this was a problem....

If restarting with addons disabled didnt do this, why did a new profile fix the problem?

Could be a problem with the prefs or the extension registry files.

Delete the extensions.* files (e.g. extensions.json, extensions.sqlite, extensions.ini) and compatibility.ini in the Firefox profile folder to reset the extensions registry.

• https://support.mozilla.org/kb/Profiles

New files will be created when required.

See "Corrupt extension files":

• http://kb.mozillazine.org/Unable_to_install_themes_or_extensions
• https://support.mozilla.org/kb/Unable+to+install+add-ons

If you see disabled or not compatible extensions in "Firefox/Tools > Add-ons > Extensions" then click the Tools button at the left end of the Search bar to check if there is a compatibility update available.

If this hasn't helped then also delete possible addons.json and addons.sqlite files.

Deleted the three extensions files, and the addons.json file. I could not find the addons.sqlite file in my profile (I dont know if this is only for older profiles or not). Still couldnt add any themes.

At any rate, Im going to work with my new FDE profile now. I can change and add themes, and I can import a couple of extensions settings and install them all easily enough.

Cor el, thanks for the time. I do like to run FDE so the Mozilla folks can use the data from my installation to make it better, but I do need to have basic functionality (or else I go back to beta).

Think I figured it out. I was also running a beta version of ABP. When I first set up my new FDE profile and found I could install new themes, I had not yet installed ABP beta yet. But after I did, I went back just to make sure, and lo and behold I could not install any more. Even installing the release build of ABP didn't do anything, so Im assuming the development build was doing something....

At any rate, yet a new profile, and I can install new themes. Unless the same problem strikes again, Im going to assume that ABP was doing something to my profile folder.

Forget it. Im back to beta.

A third new profile and no ABP,. and I still got this problem. Even the current release of ABP did, so I didn't install it at all--same problem.

I'm on beta with ABP and Im fine. Im just going to stay away from Aurora. Too many bugs and I dont do this for a living.

Thanks anyways Cor el.

Note that what you are trying to install are not actual themes but more like toolbar wallpaer. The real Themes are at https://addons.mozilla.org/en-US/firefox/complete-themes/

However many of the complete themes may not work properly in theming things on the more unstable developmental channel Aurora (Developer Edition) and Nightly.

Aurora and Nightly are meant more for Testers and Devs and not stable use as they get checkins almost everyday and get updates each of those days and therefore can have issues due to a checkin(s) until fixed or finished

Found out it was e10s. With that disabled, I was able to install themes.