Rated 1 out of 5 stars

Από τον/την D j στις Μάιος 14, 2021 ·

Don't waste your time with TH v. 68. Doesn't work at all.

από τον DaveRo (δημιουργός) στις Μάιος 16, 2021 ·

It's not clear if you mean Thunderbird 68 doesn't work, or just this addon.
I just installed TB 68.12.1 and installed the addon. It works fine.
Maybe you have other addons that interfere.
TB 68 is still used by people who rely on addons that are unavailable in 78.