Have you checked that all the cables to the motherboard and drives are properly connected, by disconnecting and reconnecting them?
A blinking amber power switch LED means the computer is receiving electrical power, but an internal power problem might exist.[br]
It can indicate a [link|https://www.minitool.com/news/how-to-tell-if-psu-is-failing.html|bad power supply], in most cases, getting a new power supply will fix the issue.