E21033 — SIPTrunkAPIKeyNotEligible

This API key cannot authenticate the trunk, so it cannot be allowed on it.

A key needs the voice permission at write level, and must not have expired, to authenticate a trunk over SIP Digest. Add the permission to the key you want to use, or choose one that still has it, then set the allowed keys again. Adding the permission is enough on its own, and the key keeps the secret your systems are already configured with.