Fix wordpress site - does not work after changing the hosting

There are three websites – two on WordPress and one on a custom CMS
After the transfer to the new hosting (transferred files and database, changed config) all three stopped working
Must be fixed

On the old hosting, the PHP version was 7.2
On the new - 8.1
If you replace 8.1 with 7.2 on the new one, then all three sites begin to work.