Hello,

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Start Firefox in Safe Mode {web link}

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

Do builtin Firefox buttons like the three-bar menu button and the three-dot Page Actions button and the Back/Forward button display a proper window if you open these?

Note that in Safe Mode all extensions are disabled, so it isn't possible to check for issues this way. You would have to disable all extensions and then enable one at the time to see whether their drop-down window is working.

You can try to disable hardware acceleration in Firefox.

• https://support.mozilla.org/en-US/kb/performance-settings

Hello ericfunk,

When you click on the icon(s) a second time, do they still show a blank window  ?

I don't know if you have many add-ons, but you could try the Console in the add-on debugging tools and see if any failure messages appear there when clicking the icon :

https://developer.mozilla.org/docs/Mozilla/Add-ons/WebExtensions/Debugging

McCoy said

I don't know if you have many add-ons

'Just noticed that you have 8 add-ons - would be a lot of work to check them all in the console .....

I solved the issue although I never found out what was wrong.

I had to completely remove Firefox and all preferences using a programme like AppCleaner.

After I reinstalled Firefox the add-ons are all displaying a correct dropdown menu.

What was wrong will remain a mystery, but : well done  !

Would you please mark your last post as Chosen Solution  ? ("Solved Problem" button to the right)