Hello! As the title implies, my external monitor that I am using with my laptop won't wake from sleep when turning on/waking up my laptop. I'll try to give as much background as possible and the steps I've taken so far to try to fix the issue.
I have an Asus ROG Zephyrus M GU502GU laptop (Windows 10, 64 bit, up to date) with an NVIDIA GTX1660Ti. I used to have an old HP monitor that worked fine with no issues. I wanted a better gaming monitor, so I bought an ASUS VG259QM. If the laptop is turned off or goes to sleep, the monitor recognizes there is no input and also goes to sleep. But when I wake the laptop up, the monitor stays asleep. Manually turning it off and on shows "no signal" and the monitor goes back to sleep. Cycling through my display settings to "PC Screen Only" seems to reset things, after which duplicate/extend/2nd screen only works just fine. It just has to manually be done every time. Removing and re-attaching the HDMI cord also gets the signal to reach the monitor.
My troubleshooting so far has involved switching to a new HDMI cord (didn't work), switching HDMI ports (didn't work), updating the drivers for Intel, NVIDIA, the ASUS laptop, and the ASUS monitor (no change for any). I've also tried factory resetting the monitor. Can't manually do a firmware update because there are no USB ports on the monitor.
Now for some diagnostic information I've gathered. When the monitor is connected to my laptop, Intel Graphics control panel only recognizes my laptop screen and NVIDIA control panel only recognizes the monitor. My theory initially was that without Intel recognizing my monitor, the computer can't wake the monitor from sleep, so I tested it by hooking my laptop up to my wife's Dell monitor. Her monitor woke up just fine, and the two graphics control panels behaved identically. I tried disabling the Intel display adapter and reconnecting my monitor. My computer lost the ability to sleep and it didn't fix the issue.
I tried my wife's laptop with my monitor. It's a Surface with a GTX 1050. Works fine. When her laptop wakes up, my monitor wakes up.
Now here's the twist: could it be a bum unit? It's actually my second monitor. I previously had the Asus VG258QM. It had the same issue of not being able to wake from sleep. I also didn't like the TN panel. I returned it and paid extra for the IPS display. Now my screen looks nicer, but is still just as useless.
I have heard of people disabling fast boot in the BIOS to solve this issue, but I tried it and it also didn't work.
My wife's computer works with my monitor and my computer works with her monitor just fine. But my computer won't work with my monitor. If anyone has any suggestions on how I can make my monitor and laptop play nice, I would greatly appreciate it. Thank you.
EDIT: I have also tried disabling the Link State Power Management