Error 0x803c0103 is a common Windows 11 update error that prevents users from successfully installing updates. It typically indicates issues with system files, corrupted update components, or problems with the Windows Update service itself.
net stop wuauserv
net stop cryptSvc
net stop bits
net stop msiserver
net start wuauserv
net start cryptSvc
net start bits
net start msiserver
sfc /scannowand hit Enter.
services.msc, and hit Enter.