All-in-One 27'' computer, there is only one HDMI - connect to monitor, there is no signal

[WF9981]

using HDMI port connected to monitor, no signal. this PC only one HDMI port. The monitor is for HDMI cable.  when I connect my laptop, it works. but when I connect to All-in-one PC, there is no signal.  I did download the driver for the monitor. when I using setting. it shows 1, and 2. if I click the 1, it shows. when I click the 2, no sign. (display not detect). please help me to resolve this issue. 

[TheOldMan]

To get proper help, the model number of the AIO is needed.  Some AIO's with HDMI have that port enabled to be an input. (so the monitor screen can be used with some other devices)  So using a HDMI connection on that port will not give you an output for a different monitor.  If that is how the AIO that you have, is setup, then an external monitor can still be connected using a device similar to this:

https://www.amazon.com/Plugable-Graphics-Multiple-Monitors-2560x1440/dp/B01C6HBJOA

[WF9981]

HP Omni 27 PC. Serial No 2MD25002BC

PRODUCT NO C1B23AV#ABA

[TheOldMan]

Looking at the support documents for that model seems to indicate the HDMI port found in the manual, page 6,  with a picture

The right side of your computer may contain an HDMI port and volume control buttons

http://h10032.www1.hp.com/ctg/Manual/c03249321

So that is an input, for connecting something to use the PC screen, such as a gaming console.

[WF9981]

YES, I did check the manual. but how this would help me? I connect right side the HDMI port using HDMI cable. there is no signal into monitor. if I use this same HDMI cable connect to my laptop. it is OK

[WF9981]

you mean my PC that HDMI is the input. it would not for extended monitor

[TheOldMan · Accepted solution]

Yes, that is an input.  It will not extend the desktop for an external monitor.  You can use the device I mentioned in an earlier post for an extra/additional monitor, however.