That is flashing for diagnostics. When the computer can't boot because of problems with it's hardware, or it has a non-software related issue that it can't report to the OS, it flashes the power button light in a sequence so you can diagnose the problem easier. In the manual, on page 72, we can see all the possible sequences that it could flash in. From your video, we can see it flashes 3 amber, then 1 white indicating a CMOS battery failure. Replacing the coin battery on the motherboard in the computer should do the trick. You will need a new CR2032 coin battery such as this one.