The domain subscription cancellation order fails with an error:
Removing of Service of Subscription #XXXXXXX is failed. Deletion service of Subscription #XXXXXXX failed.
In the DOMAINGATE.log a different error can be seen:
"Selecting Domain for notification is not allowed for Domain where Domain Status is Canceled, Not Notified."
The domains in the status canceled, not notified cannot change its status to any other. The domain got this status as a result of POA issue - resource "DNS Hosting" usage becomes incorrect if the method addDomain is executed for the existing domain with DNS hosting, therefore the system logic gets broken, the domain goes to that status.
To avoid an issue from happening and fix all the affected subscriptions - update to POA 5.4.15 or later.
To complete the current order domain conflict resolver may be used.