Client site down (critical error) after lastest

hey there, just noticed my client site is showing critical error. it did this about a month ago with Kirki as well. At the time I was advised to delete plugin and reinstall. That fortunately worked, but is not working this time.
I also came across instruction to roll back to 3.1.9. Did that, and still did not correct the site.
Any help is appreciated.

The page I need help with: [log in to see the link]