Critical error when signing in

Errors like this are logged. Check the error log on your server. If you can’t find the log, please contact your host.

Meantime, enable wp_debug and wp_debug_log and after an error, look at wp-content/debug.log to see if anything gets logged there. https://www.ads-software.com/support/article/debugging-in-wordpress/

You can also try this: Please attempt to disable all plugins, and use one of the default (Twenty*) themes. If the problem goes away, enable them one by one to identify the source of your troubles.

If you cannot access wp-admin, there are other ways to deactivate plugins:? https://www.ads-software.com/support/article/faq-troubleshooting/#how-to-deactivate-all-plugins-when-not-able-to-access-the-administrative-menus

Thanks for your answer. Although most of what you said went over my head!

I’ll try to contact the host to see if they can find the error log

And yes, I can’t access wp-admin

The WordPress critical error can have a variety of causes, though the issue often has to do with PHP. Either the PHP memory limit has been exceeded, or your plugins or themes are having issues.