Error 0x80040020

Value: -2147221472 | 0x80040020 | 2147745824

What does it mean ?

TAPI_E_NOCONFERENCE  
The call is not part of a conference.
Value: 32 | 0x0020 | 0b0000000000100000
IO_WRITE_CACHE_ENABLED  
The driver detected that the device %1 has its write cache enabled. Data corruption may occur.
Value: 32 | 0x0020 | 0b0000000000100000

Where does it come from ?

FACILITY_ITF  
COM/OLE Interface management. FACILITY_ITF is designated for user-defined error codes returned from interface methods
Value: 4 | 0x004 | 0b00000100

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Other Errors for FACILITY_ITF