Monitor doesn't wake from sleep

I plugged my monitor into Macbook over HDMI one day. It had some issues turning on in the next boot (the PC). Since then, whenever I put my PC to sleep (haven't connected the laptop to the monitor anymore), my monitor doesn't wake. So when I sleep it and then wake it in 1 minute or 10 minutes, the PC actually gets on, the fans start spinning, and my SignalRGB is set to have the RAM sticks glow white. When/if/until the OS and the apps aren't loaded, the RAM sticks are the default RGB unicorn rainbow colors. So, my PC is working. My keyboard and mouse are technically waking the PC, but the monitor says no input and goes power saving.


The worst part is even a hard reset doesn't do anything now. I turn power off, UPS off, and everything back on again, PC just refuses to boot up. SignalRGB doesn't turn on now (it's a startup app and turns RAM white even on the lock screen, but in this case, it doesn't). The only way I can turn PC on is by opening the case and reseating the RAM sticks, then the PC boots with the BIOS warning, I select Save Changes and Reset on BIOS, and it boots up fine. I've tried with Safe Mode and Secure Boot off and on, same thing.


Unfortunately I am in the habit of putting my PC to sleep. I've started doing it a lot less now but what seems to be the problem? Years of having a PC has taught me that my initial diagnosis is almost always wrong but I do believe it's either a BIOS problem or a problem with my wireless mouse. It's certainly not a display issue as I'm experiencing the same problem with a different HDMI cable and a different monitor.