When the scanproxy does not have any internet connectivity (due to firewalling issues), and the event/checkinlist has never been loaded before, a redemption request will be served with the following error-message:
{"type":"ERROR","scanType":"ENTRY","ticket":null,"variation":null,"attendee_name":null,"seat":null,"message":"Check-in list not
found","orderCode":null,"firstScanned":null,"addonText":null,"isRequireAttention":false,"isCheckinAllowed":false,"requiredAnswers":null,"position":null}
I guess, the "not found" part is technically not really incorrect - but it is a little bit misleading... The issue is not that the checkin-list does not exist but rather that the connection to the pretix-host is unavailable.