How do I fix this Wordpress error?
Questions like this require more information or atleast a screenshot to give an exact answer.
Common fatal errors might be due to memory limits being exceeded or php functions missing in your hosting. Just enable WP_DEBUG to True for finding the exact issue. Check your WordPress error log and server error log for more information.
Over the years, we have found most of these errors are from updated plugins so start there.
Still not able to find the solution, simply switch to a Managed Hosting provider who will take care of everything for you.