Error 0x80EF01F6

Value: -2131820042 | 0x80EF01F6 | 2163147254

What does it mean ?

RTC_E_STATUS_SERVER_BAD_GATEWAY  
Bad Gateway
Value: 502 | 0x01F6 | 0b0000000111110110

Where does it come from ?

FACILITY_SIP_STATUS_CODE  
SIP - Session Initiation Protocol (VoIP)
Value: 239 | 0x0EF | 0b11101111

Other Errors for FACILITY_SIP_STATUS_CODE