Thunderbird PGP manager doesn't work

In the latest version of Thunderbird apparently available to Qubes (I think this qube is based on Debian 11, and Thunderbird is v 91.11.0), the PGP manager won’t import any more of my public or private keys. Has anyone else experienced this, know of a way around it, or know of a way to make it update to a newer version?
Thanks!