Thanks!

Update – I removed the plugin folder before and the issue persisted, which is why I posted this here. I found the blacklist in my DB, emptied it out, and my site now loads. Is there a limit on how many can be added? I was not able to find any unusual strings or characters.

Do you see any PHP errors in your error_log file?

[ Signature moderated, please don’t use those here. ]

After getting the site back up we went through the contents of the blacklist to see what may have been the issue. We have a small script we run to try to extrapolate suspect IPs, focusing heavily on repeat lockouts. Turns out someone here was trying to log in, constituting a false-positive, and after they tried a bunch of usernames that all failed the IP was added to the blacklist. In short, we added one of our internal IPs that should have been whitelisted and blocked ourselves.