Media Library just gives me a spinning dot

This may be a plugin or theme conflict. Please attempt to disable all plugins, and switch to the default Twenty Twenty theme. If the problem goes away, enable them one by one to identify the source of the problem.

If you can install plugins, install Health Check. On the troubleshooting tab, you can click the button to disable all plugins and change the theme for you, while you’re still logged in, without affecting normal visitors to your site.

There have been no changes to WordPress since before this came up except for an update to WP5.4 and the addition of CFF. I deactivated CFF so that can’t be the issue. The rest has been stable long before the Media Library issue came up. Not sure if I can downgrade WP but if that was really the case others would have noted the bug.

Please try the steps I posted, thank you.

Great. Installed Healthcheck and immediately got the following error:

There has been a critical error on your website. Please check your site admin email inbox for instructions.

Learn more about debugging in WordPress.

Now we can’t access our admin log in for WP.

I used FTP to delete the Healthcheck plug-in and was able to get back into our server. Tried again to install Heathcheck with the same results. Deleted again with FTP. Very strange.

Sounds like you have a very critical problem in your installation. Health Check is one of the core plugins, one of our safest following a full re-write over a year ago, and safely recommended here often.

Try downloading WordPress again, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel (consult your hosting provider’s documentation for specifics on these), and delete then replace your copies of everything on the server except the wp-config.php file and the /wp-content/ directory with fresh copies from the download. This will effectively replace all of your core files without damaging your content and settings.

Some uploaders tend to be unreliable when overwriting files, so don’t forget to delete the original files before replacing them.

Thanks. I’ll give that a try. I did reinstall 5.4 from within WP, but that didn’t help.

Based on a plug-in issue that seemed unrelated, suggested solutions turned out to be the fix for that and this problem.

I found 500 errors in the Apache log and out-of-memory errors in the PHP log. The PHP configured memory limit was 32MB, although there was an 8MB reserve amount. I increased the memory limit to 128MB and all the issues disappeared.