An IP address gets ‘Forbidden’ for wp-login but not the public homepage

An IP address of a regular commenter somehow now gets a ‘forbidden’ response when trying to access the login screen. The error says ‘Forbidden. You don’t have permission to access /wp-login.php on this server’. If I connect the same computer via phone tether it works fine.

This IP address was responsible for some spamming a few weeks ago that we think might have triggered it. However, now we’ve got a social fix for that problem, there doesn’t seem to be a setting anywhere to reallow the IP, or confirmation in the dashboard that they even are blocked. There’s no ‘blocked IP’ box anywhere with this particular IP address in it.

We don’t have any kind of blacklist plugin. We do have Akismet on the site, but it doesn’t have any blacklist section on there.

Any ideas where the block might be?