Issue after Disabling Directory Listing

Disabling listing alone wouldn’t have changed WP operation in any way. It is possible you inadvertently changed something else in .htaccess, or saved it using the wrong character encoding, or failed to use a plain text editor to make the change.

Your best option would be revert to the backup file you hopefully made prior to making any change. If that’s not an option, you can see if WP will recreate one for you. Rename the current .htaccess file. Go to your permalink settings and re-save your settings. WP should create a new .htaccess file if it’s able to. You can then very carefully attempt to disable directory listing again, this time keeping a backup ??

Don’t be surprised if the problems persist with a WP generated .htaccess file. Something else is wrong and your edit was coincidental. To get more clues about the cause, check the error log, your browser console, and site health.