[solved] particular remote account not available on whole instance
I am running Pleroma 2.5.1 (OTP 23.3.4.18) and my instance does not "see" a particular remote account on social.cologne. The account in question is @koeln@social.cologne. Search, interaction, nothing works. It feels like this particular remote account does not exist. Other accounts on social.cologne are discoverable and interaction is not a problem. I am already in contact with the admin of social.cologne. He has found no problem on his end.
Where and how do I best get started with troubleshooting?