Try the following:
Hit Windows logo key + r to open Run.
Type in regedit and hit Enter.
In regedit, select (top of left pane) Computer then File> Export. Export the registry backup to a convenient location. Right-clicking> Merge that REG file will restore the pre-edit registry should something go wrong and you're unable to simply re-edit the ForegroundLockTimeout DWORD to it's previous value.
Also... For additional safety, create a Restore Point. Restoring to that point will restore the previous registry.
In regedit navigate to
HKEY_CURRENT_USER\Control Panel\Desktop
Right-click the DWORD Value ForegroundLockTimeout, select Modify> Base: Decimal and change the value from 200000 to 0 (zero)
Exit Registry Editor then restart the computer.
If this doesn't resolve the issue, return the value of the ForegroundLockTimeout DWORD to Decimal 200000.