Dell 5090 orange light turns on (not flashing) when pressing power button

Is there any white LED light codes follows the amber light?  There is blinking pattern of 1 amber, 2 white indicates unrecoverable SPI flash failure.  Describing of event or symptom prior to the issue will help with troubleshooting.  Not knowing which form factor you have, this is OptiPlex 5090 tower diagnostic LED behavior:  https://www.dell.com/support/manuals/en-us/optiplex-5090-desktop/opti5090mt_sm/diagnostic-led-behavior?guid=guid-07853ede-4844-43b1-8f55-6d1a070dd898&lang=en-us

if your pc works perfectly other than the strange power button led, then you can ignore the orange led on power button.