Identify which stage failed
Can the caller reach the correct greeting? Does a message appear in the mailbox? Can the user retrieve it? Does the phone show a waiting-message indicator? Treat each answer as a separate branch rather than resetting the phone immediately.
A message-waiting or email fault can occur even when the recording was saved correctly.
If the greeting is wrong or missing
Check the unanswered-call destination and the mailbox context. Confirm the mailbox exists and the call reaches the intended application. On FreePBX, inspect the extension voicemail settings and GUI routing; avoid editing generated Asterisk files.
If recording or playback fails
Check mailbox capacity, filesystem space and service permissions. Compare one controlled message with the failure. If the stored message is silent, inspect the inbound media path; if it contains audio but playback is silent, investigate the retrieval leg instead.
If only notification fails
Check the phone's mailbox association and subscription behavior. Email notifications have a separate delivery path and may fail despite a valid local message. Review mail delivery evidence before changing SIP credentials. Do not expose voicemail retrieval without authentication to simplify access. Finish by testing greeting, message deposit, retrieval and notification together, then remove any temporary diagnostic capture.
Sources & applicability
Primary references for the technical details above. Operational examples and planning checklists are VoIP.info editorial guidance.
Examples require adaptation to your topology. No live PBX or hardware testing is claimed.