Why is Apple Intelligence stuck at 0% downloading?

I have an M2 MacBook Air running macOS sequoia 15.3.1 and my Apple Intelligence support won't download. I've tried changing my language as suggested in other forums and nothing helps. It will show downloading 0% and then after a while it will switch to 100% but it never finalizes and the Apple Intelligence features won't work.

[Re-Titled by Moderator]