For me, the plugin was running successfully with the 68 pre-release version in the discussion linked. Since the last update, Thunderbird blocks its once more saying it's not compatible anymore. Please help! :)
If you feel adventurous, you could test my similar add-on Birthday Calendar. I did not yet perform enough testing to consider it stable (and upload it to the official add-on store), though.
Discussion started already in https://github.com/ingomueller-net/ThunderBirthDay/issues/14, but I think it's worth opening a new issue for the new version 78.
For me, the plugin was running successfully with the 68 pre-release version in the discussion linked. Since the last update, Thunderbird blocks its once more saying it's not compatible anymore. Please help! :)