Upgraded to PHP 7.4 and now I can't edit my pages

My website was built on WordPress using XTheme Pro. To make sure I’m using the latest and greatest, I wanted to move my site over to PHP 7.4. I made backups, downloaded everything there is to save, and made the change.

Now, I can edit any and everything except my page content. My theme just gives me the spinning wheel of death. Any suggestions?