Order cancellation (or cancellation order) fail with an error message:
No response from the backend
The same is seen in the logs:
#101 DB Connection fatal error: ODBC error #08S01: No response from the backend;
Such error usually occurs because method
ServiceDestroy fails with an exception. There are two related bugs - PBA-36214 ("Not possible to cancel an order when there is no account in POA") and PBA-36014 ("Cancellation of SO with services based on PEMGATE fails with "No response from the backend").
Fins an actual error from POA side - PEMGATE.log or poa.debug sahll reveal it. Resolve an issue from POA side and then try cancel the service again.