HP Monitor attached to Mac displays error message in sleep mode

[Udub]

My HP Monitor attached to my MacBook Pro used to sleep (screen all black) when the Mac was sleeping.  In the last week, when the Mac is in sleep mode, the HP displays an error message ("No Signal Detected").  How do I get the HP to sleep (go all black) when my Mac is sleeping?

[A4Apollo]

Hi! @Udub, Welcome to HP forums.

I understand the monitor is connected to your MAC PC when the MAC goes to sleep you get an error on the monitor "No Signal Detected".

Don't worry I'd like to help you out.

How is the monitor connected from the MAC?

Have you tried connecting the monitor to a different PC and check if the issue persists?

If you are using any adapters try using a different adapter and check if it helps.

Please try the steps recommended below.

Cycle the power on the monitor as follows:
Turn off the monitor. The power light on the monitor should be off. Leave the computer turned on.
Unplug the power cord.
Wait 5 seconds.
Plug in the power cord.
Press the power button on the monitor to turn on the monitor.

Try restoring the monitor back to factory settings and check if it helps.

1. Allow the monitor to warm up for 30 minutes before adjusting.
2. Access the OSD menu, then select Image Setup.
3. Set the main Clock settings correctly first, because the Phase settings depend on
the main Clock settings.When adjusting the Clock and Phase values, if the
monitor images become distorted, continue adjusting the values until the
distortion disappears. To restore the factory settings, access the OSD menu,
select Factory Reset, and then select Yes.

Refer this article to further troubleshoot Monitor is Blank issues.

If the issue still persists after trying out the steps it could be an issue with the cable, adapter or the MAC itself.

Replace any of these parts and check if it helps.

I'll keep an eye out for your response.  

I hope you have a great day! 🙂