Triode / RichieZed’s Spotify Family app hasn’t been updated since 2017, and will most like not be updated anymore.
Michael Herger created therefore a plugin called spotty which also supports Spotify’s families account. I would suggest that you ditch the Spotify Family plugin and use the „Spotify/still spotty“ plug-in in LMS. I run 7.9.2 here on my PI server and it runs just fine !!! -:)