Why is my iPhone not backing up to iCloud?

Hi!

My problem is that the phone (Iphone 15 pro) can't do backup to icloud, if i choose to manually update, the progress bar goes for about 1/5 progression than it gets stuck there, and the estimated time remaining is starts to increase. It has stabile internet connection, and once i left it on charger while trying to update for about 16 hours, nothing happened, only the estimated time gone up.

I tried to update from itunes, but the iphone icon is not showing for me in the itunes app, and reinstall wont help either.

I tried everything i found on the internet that might work, but nothing helped.

Any suggestions?

Oh, and it worked before just fine, the problem started about 9 weeks ago.

[Re-Titled by Moderator]