ERROR_INVALID_USER_PRINCIPAL_NAME 0x800721BC

Error code 8636 · HRESULT 0x800721BC

WINDOWS

The User Principal Name (UPN) is invalid.

Windows troubleshooting diagram: Device Manager warning and a system file scan
Windows errors: check drivers, system files and Event Viewer, in that order.

What it means

ERROR_INVALID_USER_PRINCIPAL_NAME is a Windows error code (system error 8636, returned as HRESULT 0x800721BC) reported by Windows. Its official message is: “The User Principal Name (UPN) is invalid.”

How to fix ERROR_INVALID_USER_PRINCIPAL_NAME

  1. Reboot once — many one-off system codes disappear with a clean restart
  2. Repair system files: 'sfc /scannow' then 'DISM /Online /Cleanup-Image /RestoreHealth'
  3. Find the source in Event Viewer → System: filter for this exact code and open its provider link

Related errors

ERROR_INVALID_USER_BUFFERERROR_DS_FLAT_NAME_EXISTS_IN_FORESTERROR_DS_OID_MAPPED_GROUP_CANT_HAVE_MEMBERSERROR_DS_DOMAIN_NAME_EXISTS_IN_FORESTERROR_INVALID_DATAERROR_WRITE_PROTECTERROR_NOT_READYERROR_CRC

Source: Microsoft WinError.h

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