OS patch updates not installing on Windows servers

One of the reason could be corrupted OS files. Open the CMD as administrator and run the SFC /SCANNOW command. This should replace any corrupted OS files which are preventing the OS patch updates. Once done now manually try installing the Windows patch updates and restart the system/server after this. Note: The patch updates to work properly, the C drive should have enough space. I would recommend to have atleast 15 gb of space for this.