Monitor Will Not Sleep While Computer Is Locked

I've recently ran into this problem on my computer. My monitor will not sleep while the computer is locked. If I just let it sit, the screen saver will appear, then the monitor will sleep. However, once the computer is locked, the monitor will not sleep.The monitor auto sleeping was working perfectly fine last week.I have triple checked the Power Options, ensuring the monitor sleeps in 10 minutes (screen saver activates at 5 minutes). I've also looked at the Advanced Power Options setting, and that is set at 10 minutes as well. I have reset to defaults and the problem still persists. I have also tried to set a GPO to see if that would work, nothing either.how the monitor will sleep when the computer isn't locked.I know I could just sleep my computer (I don't want to) or turn my monitor off (this gets annoying after a while).

Edit: What I've done/tried:

Triple checked monitor settings/power options
Reset to defaults, then set the monitor to sleep at 10 minutes
Changed to a new theme
Enabled monitor sleep GPO
Restarted multiple times
Disabled screen saver
My monitor has no sleep settings (settings, not function; it has the sleep function)