Check HDMI in

[MEL66A]

Had power outage screen shows check HDMI IN, computer will not boot up.

[Echo_Lake]

@MEL66A
Thank you for posting on the HP Support Community.

Don't worry as I'll be glad to help, I have a few troubleshooting steps we could try to fix the issue:  

I suggest you do a Power Drain. Shut down the AIO computer and remove the AC Adapter. Press and hold the power button for 15 seconds without any power source. This will drain out any static charges from the AIO Computer.

Restart the computer and if you still see the " check HDMI cable " message, please check and press the HDMI Source Button to switch the display.

Please refer to this picture to locate the HDMI Source Button ( No 5 ).

1. Webcam and microphones

2. Screen

3. Optical disk drive

4. Power button

5. HDMI source button

6. The bottom I/O ports

7. Speakers

Hope this helps! Keep me posted for further assistance.
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