Andrew Nevins on "WordPress "is currently unable to handle this request.'"

this problem is occurred due to half sql query submission or wrong/invalid php code submitted i.e like mass data submission(Site down because of Max time execution limits) or wrong/invalid php code submitted in via post data/invalid modification of php file.

Try Uninstalling plugins one by one and refresh your website and see which plugin is causing the problem. Worked for me!

I have same error and deleted all plugins using ftp still my site is not working