There is an updated version of the add-on, too. Remove the current one and fetch the new one.
This was an odd "really major" jump in Thunderbird version and just like Thunderbird had not been self-updating a lot of the add-ons weren't, either.
Brian - Windows 10 Pro, 64-Bit, Version 2004, Build 19041
It’s hard waking up and realizing it’s not always black and white.
~ Kelley Boorn