The remote node couldn't fulfill the request for a reason not covered by a more specific code (DIAMETER_UNABLE_TO_COMPLY) — usually indicates an internal/configuration issue on the responding side.
Where you see it
In the Result-Code or Experimental-Result-Code AVP of a Diameter answer (S6a, S6d, Gx, Gy, Cx…).
What to check
Request internal logs from the responding operator — this code doesn't give the exact detail, it has to be requested directly.
Look at the Origin-Host of the answer: an intermediate agent (DRA/IPX) and the home HSS mean different owners of the problem.
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