Unable to activate Windows screensaver

After playing Metro Exodus, having mashed the keyboard a couple of times during gameplay, I found that the screensaver would not work.

No matter what I tried, I could not get it to come on:

1) GPEDIT User Configuration/Administrative Templates/Control Panel/Personalization/Enable Screen Saver and set it enabled.
2) Enabled Screen Saver Timeout in same.
3) Used your .reg file Enable/Disable Screensaver.
4) Used regedit in HKEY_Current_User\ControlPanel\Desktop.
5) sfc /scannow (no errors).

The only way it would activate is by restoring a full backup via Macrium. I checked the group policy and registry entries after backup and they all looked the same as before the backup.

Where does the 'screensaver' itself reside? Could something like a key combination have a permanent effect on disabling it? Could something be corrupted and sfc missed it?

Running Win 10 Pro v 1903. Hope someone can shed some light on this.

Thanks.

If your power policy turns the monitor off in a shorter time than the screensaver it will never come on

Power is set as:
Sleep - Never
Turn off Display - 10 minutes
Screensaver on - 5 minutes