That's weird. I can't find anything relevant in the seclog either, other than it was accessed in 2018 prior to this.

Is there an email together with the ban notice? Can you sign from any of the addresses below:

Send an email to the email address stated and prepare a signed message for that. Instructions are in this thread[1].

[1] https://bitcointalk.org/index.php?topic=5089777.0