Yes wrote:

When I press the on/off button for the pc on the front of the case, I
see it start to light up but within a fraction of a second, it shuts
down is the best way I can describe it - does not continue to boot
up. When I press the on/off button again, nothing happens.

Take off the side panel from the case. When you press the Power button
to turn on, does the CPU fan spin? If not, the BIOS will see it has
zero RPM (no speed) and immediately shutdown to protect the CPU from
burning up (and possibly taking out regulators and other parts on the
mobo next to the CPU). If you removed the CPU fan's cable from the mobo
and put it back on, make sure you got it aligned properly. There is a
polarizing tab but it's just a plastic flange that can bend out, so it
is still possible to misalign the cable on the connector. If the RPM
(sense) wire is broken, the BIOS will also see no RPM for the CPU fan.

If the CPU fan doesn't spin, maybe it's bad and needs to be replaced.
Make sure something isn't obstructing its fins, like a wire or cable
hitting the fan and slowing it down or stopping its rotation altogether.

If you see the CPU fan start to spin after pressing the Power button but
it immediately stops along with the computer shutting down, the fan is
probably okay - but the PSU may not be.

Since you were digging around inside the computer, make sure all
connectors are fully seated, the CPU and GPU fans spin up (even if
momentarily), the memory is fully seated (although you usually hear a
beep for bad memory unless there is no speaker or it is disconnected or
has failed).

"ASUS AMD mobo" is insufficient to tell anyone just WHAT you actually
have. Give a model number. Some of those have diagnostic LED displays
on the mobo that will show an error code.