very new TTG user.
Similar to #29 - but also different. I had two small simple tab groups set and I tried to restart ff to experience how the extension handles this. I had the TTG settings tab closed at the time. I did not have the ff option to "Restore Groups after Browser Restart". When I restarted the browser I was prompted on whether I wanted to restore and I said yes. After this, I got one window with the set of tabs IIRC were the several that were un-hidden when I had closed. When I click the extension icon all I can see now is "Stash" with no other options:

My other tabs are present when I looking at the hidden tabs, and when I select one of them, I get the whole group they were in unhidden, and the ones that had been previously visible get hidden (same behavior as reported in #29). But the extension button's behavior remains unchanged - I can't see any group titles nor get to settings.
FF v95.0.2 on MacOS 12.0.1 with TTG 0.18.24. I previously had Sidebery loaded but disabled that extension and closed all but a few tabs before adding ttg. No other tab management stuff or other extensive extensions in play (just coming back to FF after getting sick of Chrome\Edge)
Please enter about:devtools-toolbox?id=%7Bdcdaadfa-21f1-4853-9b34-aad681fff6f3%7D&type=extension in the url bar after the tabs fail to restore, select the console tab, and see if there are any errors.
I do see some things here, no idea what they mean:

I haven't tried to repro, I'm still in this weird state and I'm not entirely clear how to get TTG working again, I have not tried restarting the browser again - but I will probably try random things to see whether I can get it back to normal next.
very new TTG user.
Similar to #29 - but also different. I had two small simple tab groups set and I tried to restart ff to experience how the extension handles this. I had the TTG settings tab closed at the time. I did not have the ff option to "Restore Groups after Browser Restart". When I restarted the browser I was prompted on whether I wanted to restore and I said yes. After this, I got one window with the set of tabs IIRC were the several that were un-hidden when I had closed. When I click the extension icon all I can see now is "Stash" with no other options:

My other tabs are present when I looking at the hidden tabs, and when I select one of them, I get the whole group they were in unhidden, and the ones that had been previously visible get hidden (same behavior as reported in #29). But the extension button's behavior remains unchanged - I can't see any group titles nor get to settings.
FF v95.0.2 on MacOS 12.0.1 with TTG 0.18.24. I previously had Sidebery loaded but disabled that extension and closed all but a few tabs before adding ttg. No other tab management stuff or other extensive extensions in play (just coming back to FF after getting sick of Chrome\Edge)
I do see some things here, no idea what they mean:

I haven't tried to repro, I'm still in this weird state and I'm not entirely clear how to get TTG working again, I have not tried restarting the browser again - but I will probably try random things to see whether I can get it back to normal next.