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WPN_E_CALLBACK_ALREADY_REGISTERED
WPN_E_CALLBACK_ALREADY_REGISTERED is an HRESULT used by the Windows notification platform. It means that code attempted to register a notification callback when the platform already has a callback registration for it.
What to check for WPN_E_CALLBACK_ALREADY_REGISTERED
- Register the callback once and share it across components that need notification events.
- Unregister or replace callbacks only through the documented lifecycle API.
- Protect registration with synchronization when startup and background activation can race.
Diagnostic interpretation
This result has the HRESULT value 0x803E0206. AllStat records the condition as “Notification callback interface is already registered.”.
Evidence to capture
- Capture any IErrorInfo text, activity identifier, event-log entry, and subsystem trace that mentions this result or the wpn / callback / already / registered operation.
- check the documented return contract of the specific API because the same HRESULT can require different recovery in different interfaces.
Retry and recovery
” has changed.
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