Hello! I'm the upstream maintainer of Deja Dup. Google
will be removing a particular oauth workflow that Deja Dup uses in
September.
This means that any new authentications for users trying
to connect Deja Dup to their Google account will fail after that date
(existing users that have already authenticated themselves will continue
to work).
If possible, updating to 43.3 will fix this. But for older
releases (Guix is on 42.8 at time of writing, I believe), I recommend a
backported patch.
Here's a wiki page for more information about the issue, including backported patches for older versions: https://wiki.gnome.org/Apps/DejaDup/GoogleAuthChange2022