Cause 1: DisplayPort Sleep Handshake Failure (Most Common)
What's actually happening here is your GPU stops sending a hot-plug detect signal when the monitor enters deep sleep, and when it wakes, the two never renegotiate the link. HDMI doesn't have this problem because it uses a different handshake. DisplayPort does. That's why the same monitor works fine on HDMI and dies on DP.
You'll see this most often on Windows 11 23H2 with an Nvidia RTX 30 or 40 series card, and on some AMD RX 6000 cards running Adrenalin 23.x drivers. The monitor goes black, the OSD says "No Signal" or "DisplayPort No Signal," and moving the mouse does nothing. Power-cycling the monitor alone doesn't help. Unplugging and replugging the DP cable sometimes does, which is the giveaway.
The real fix is disabling DisplayPort's deep sleep behavior. Two places to do it:
- Monitor OSD: Look for a setting called "DisplayPort 1.2," "DP Deep Sleep," or "DP Hot Plug Detect." Turn it OFF. On Dell U-series and LG UltraFine monitors, this is under Menu → Input → DisplayPort. On some BenQ and ASUS models it's called "DP Power Save."
- Windows: Open Device Manager → Monitors → right-click your monitor → Properties → Power Management tab. Uncheck "Allow the computer to turn off this device to save power." If the tab isn't there, your monitor driver is using the generic Microsoft one and you need the vendor INF.
If the monitor OSD has no such option, you're stuck with the cable workaround: pull the DP connector from the GPU, wait five seconds, plug it back in. Annoying, but it forces a new HPD cycle.
Cause 2: The Cable Is Wired Wrong (Pin 20)
Cheap DisplayPort cables — usually the ones bundled with monitors or bought for under $8 on Amazon — often have pin 20 connected when the spec says it shouldn't be. Pin 20 carries 3.3V power, and when both ends are powered, it creates a backfeed that confuses the source detection circuit. The monitor thinks it's being powered by the GPU, the GPU thinks the monitor is off, and you get a black screen with a "No Signal" banner.
This shows up more than people realize. The symptom is often intermittent: works on cold boot, fails on wake from sleep, or works with one cable and not another identical-looking one. If you swap the cable and the problem vanishes, that was your cause.
Cable Matters, StarTech, and Club3D make VESA-certified DP 1.4 cables. Anything without a certification listing is a gamble. Buy one of those, not the $6 generic.
Also check cable length. Passive DisplayPort 1.4 tops out around 2 meters at full bandwidth (HBR3, 32.4 Gbps). Beyond that you need active cables. A 3-meter passive cable driving a 4K 144Hz monitor will drop the link and register as no signal during heavy bandwidth moments — usually when you open a game or a video editor.
Cause 3: GPU Port Priority or MST Conflict
Some GPUs default to a priority output. If you're running two monitors and the secondary one shows no signal at boot, the GPU may be trying to hand off to a port that isn't connected. Nvidia's driver in particular has a quirk where the DisplayPort output nearest the HDMI port is enumerated first, regardless of what's actually plugged in.
The fix is to force the port order or disable Multi-Stream Transport if you don't need it:
- In Nvidia Control Panel → Display → Set up multiple displays, make sure both monitors show as detected. If one is missing, click "My display is not shown" and force-detect.
- In the monitor OSD, turn off DisplayPort MST if you're only running a single monitor off that port. MST is for daisy-chaining and adds a negotiation step that can fail.
- On AMD cards, disable "DisplayPort Alternate Mode" in Radeon Software if you're not using USB-C DP alt mode.
Daisy-chaining is a special case. If you're running monitor → monitor via DP-out to DP-in, the middle monitor must support MST and must be set to DP 1.2 or higher in its OSD. Setting the middle monitor to DP 1.1 breaks the chain, and the downstream monitor shows no signal even though the middle one works fine.
Quick Reference
| Symptom | Likely Cause | Fix |
|---|---|---|
| No signal after sleep/wake | DP deep sleep handshake | Disable DP Deep Sleep in monitor OSD; disable device power-off in Device Manager |
| Intermittent, cable swap fixes it | Pin 20 backfeed on cheap cable | Replace with VESA-certified cable (Cable Matters, StarTech, Club3D) |
| No signal only at 4K 144Hz | Passive cable too long for HBR3 | Use active cable or shorten to ≤2m |
| Second monitor missing at boot | GPU port enumeration order | Force-detect in Nvidia Control Panel; disable MST |
| Downstream monitor in daisy chain dead | Middle monitor set to DP 1.1 | Set middle monitor to DP 1.2 or 1.4 |
If none of these help, plug the monitor into a different machine. If it still shows no signal there, the monitor's input board has failed and it's a hardware repair, not a configuration problem. That's rare, but it happens — usually after a power surge or a bad batch of capacitors in the input stage on older units.