A customer is unable to receive calls on the EX90 endpoint, but can made outbound calls. The endpoint uses CUCM for call and registration. If the engineer only has remote access to the EX90 and…

If the calling party's Calling Search Space cannot reach the partition containing the EX90's directory number, inbound calls will fail while outbound calls succeed, making partition reachability a primary CUCM-side check for one-way call failure.

Checking EX90 System Status provides general hardware and network diagnostics but does not directly reveal why inbound calls fail while outbound calls succeed.

Confirming registration is a valid initial step, but since the endpoint can make outbound calls it is already confirmed as registered with CUCM, making this step redundant given the symptom.

Do Not Disturb (DND) enabled on the EX90 causes the endpoint to reject or silently ignore incoming calls while still allowing outbound calls, and this status is directly verifiable via the endpoint's WebAdmin interface without requiring physical access.

The Device Calling Search Space on the endpoint controls which partitions the device can call outbound, not which partitions can reach the device inbound, so it does not explain the inability to receive calls.