Could not unlock user

On a multi-site installation, one of the admin users was suddenly locked out yesterday with a 503 error after having been successfully logged in earlier in the day. They requested an unlock email, but it was never sent out, even though other emails were going out from the site (using Post SMTP).

As an super admin myself I looked around for a way to unblock them but could not find it, or even find in Wordfence where they were blocked. I did see something in the Wordfence documentation saying that Wordfence had changed how one could unblock a locked out user. That did not, however, include any information about how unblocking works now.

We resolved the issue by deactivating Wordfence, but I am looking for suggestions about how to reactivate it without risking the same thing happening again. I also have Wordfence installed on dozens of other sites that I support so am concerned about the same problem occurring with any of them.