Not compatible with the latest version of Thunderbird
Hello, MEGAbird 3.0 should be compatible with Thunderbird 60.7.1 (the current latest public version), so can you please provide further details, such as what versions are you using and under what OS? Also, do you see any error in the console ( open it with ctrl/cmd+shift+J ) ?

Still incompatible. Using latest Thunderbird 68.3.1
Still incompatible, using Thunderbird 68.5.0 which is at the time of writing this comment the latest stable release.
I am having the same issue
Same issue on Thunderbird 78.7.1 on Windows 10. Please fix is ASAP!
At this time of writing, Megabird is incompatible with Thunderbird 91.5.0. Pleas update the add-on to webextension standard.