iMovie not working after Monterey 12.7.6 update on 2015 MacBook Air

I’ve updated operating system on 2015 MacBook Air to Monterey 12.7.6 - now it would not open iMovie - telling me to update. When I pressed to update it said I needed to update and took me back to the exact same command to update etc. So moved app to trash and attempted to download new. It said my OS would not support latest version but I can download older compatible version. Pressed to download - now just endless cycling including continuing after restart. Please help - I need iMovie.

[Re-Titled by Moderator]