Mission Impossible Crypto- Part 2

I’ve retrieved public keys for X100, X101, X121. The one I think I need to focus on (X121) is giving me padding errors when using OpenSSL to get more info on it… and it looks like it could be a DKIM key which would seem to be even less useful. I can get ‘e’ and ‘n’ for the other two keys, which may come in handy. Hoping for a nudge on what I’m doing wrong with X121.pub.