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TAPI_E_CALLUNAVAIL
TAPI_E_CALLUNAVAIL: exact failure boundary
0x80040007 corresponds to TAPI_E_CALLUNAVAIL. The platform message is No call appearance available. This result is returned while creating or accepting a call on an address with a limited number of call appearances. The diagnostic question is whether the address cannot provide another call object or appearance at this time.
Evidence to capture
- Record this result, 0x80040007, the native method name, process and thread IDs, operation ID, component build, architecture, and elapsed time.
- Capture address type, destination form, media flags, provider capability, call state, privilege, and request or completion identifier.
- Keep IErrorInfo, provider extended status, relevant device/storage events, and the first lower-level failure.
- When handling this result, unsubscribe events, release call and terminal interfaces, cancel only live asynchronous requests, and let terminal call-state events drive final cleanup.
Likely causes to separate
- All channels are occupied.
- Provider policy limits simultaneous calls.
- A stale call has not completed teardown.
Focused diagnostic test
Reproduce the same native call with the same object identity and change one cause candidate at a time. Preserve the first provider or lower-layer result and compare object state before cleanup. A different HRESULT after one controlled change is a new boundary, not proof that the original operation is fully repaired.
Correction
wait for a call-state event or select another address; do not spin on immediate retries.
Verification
After correction, repeat the operation that returned this result. Verify the intended API operation completes and that any output, ownership transfer or persistent state is valid; do not treat disappearance of the dialog alone as success.
Technical references
- Microsoft: TAPI_E constants
- Microsoft: ITAddress:CreateCall
- Microsoft: ITBasicCallControl
- Microsoft: TAPI 3 reference
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