Hi - I have an older HP Omni 120 all in one desktop that is flashing orange at the power button.

[TongusGrump1]

Have an older HP Omni 120 that's flashing orange at the power button.  Worked great the other day and now this.  Help.

[itsmyname]

@TongusGrump1 -- hold-down the on/off button for 30 seconds, or until the computer powers-off.

Then, power-on. Does the lamp still show as orange? If so, it could be the computer's power-supply that is failing.

[TongusGrump1]

Power supply output tests out to the specs listed on the power supply bottom label. Held down the power button for 30 seconds and still does the flashing light. Bummer.

[itsmyname]

@TongusGrump1 -- bummer

Indeed. 

Is this your computer: HP Omni 120-1124 Desktop PC Product Specifications | HP® Customer Support

It was first marketed in 2012.  A nine-year-old dog is an old dog. A nine-year-old computer is an old computer.

Maybe, it is time to "cannibilize" it (removing the disk-drive that holds your files), and purchase a "ready for Windows 11" replacement.

My guess is that computers with Windows 11 preinstalled will be available by XMAS 2021.

Until then, any new computer will ship with Windows 10, with the possibility of taking the free upgrade to Windows 11.

Maybe, without the disk-drive, list it on eBay as "for parts only", to see if some other person wants your computer's screen or case or RAM or CD/DVD drive, to repair their similar-vintage computer.