Getting back in.
THE SYMPTOM
A blank page, or a fatal error, or no admin access.
THE FASTEST FIX
Rename the plugins directory using File Manager or FTP.
That deactivates every plugin at once and usually restores access.
THEN
Rename it back Rename individual plugin directories one at a time Find the offender
WHY RENAMING WORKS
WordPress cannot find the plugin, so it deactivates it.
IF THE SITE IS STILL BROKEN
The problem is not a plugin.
Check the theme, .htaccess, and the error log.
READING THE ERROR LOG
It names the file that failed, which identifies the plugin.
Frequently faster than the renaming method.
AFTER RECOVERING
Delete the offending plugin, or find an alternative.
Report the problem to the developer.
WHAT TO DO DIFFERENTLY NEXT TIME
Back up before installing. Test on staging.