Dell optiplex gx60

Blinking amber power light can mean bad PSU.  Solid amber can mean bad motherboard.

With external peripherals disconnected, if you push the PSU test button (if it has one) (with PC off), do you get the green light?  If you do, internal peripherals are good.

If not:  How to Run a Power Supply Unit Self Test On a Dell Desktop 

Dell BIST Test video 

If the power button is blinking green, the computer received good power but something is halting the boot process.  Let replace a little battery on the motherboard first before attempting with the troubleshooting process.  Most desktop computers use CR2032 coin cell battery, which cost around 1 to 2 usd.

You must use safety procedure while working inside the machine, not to cause any damage.  The machine has to be unplugged from electrical outlet and discharge of residual power.

This is the user guide for your machine, it will help to provide information to the questions you may have https://dl.dell.com/manuals/all-products/esuprt_desktop/esuprt_optiplex_desktop/optiplex-gx60_user's%20guide_en-us.pdf

He gets a green flashing light 

Pardon moi, I missed that you said "green" and automatically thought blinking light was amber.

I'd go with Chino de Oro's suggestion of replacing the battery, likely size 2032.  Not sure if the user's guide will help, but if it doesn't, you have my suggestions.

Thanks, he his now showing me in a video chat that it's looking amber now. So I will try the battery first than try each of the other suggestions to see what works.