I am not familiar with that psu.
But, unless you know it to be of good quality, that is what I would suspect first.
You are looking at repair or replace.
What is this pc used for?
On diagnosis, see if you can't borrow a known good psu to test with.
Or, buy a replacement of sufficient power that you would use in a new build.
Buy from a shop with a good return policy. Expect to pay a 15% return fee.
You will find it easier to take everything out of the case to test with.
That eliminates some possibilities of short issues.
Try testing with a single ram stick to see if you get into the bios.
Your motherboard manual will identify the slot to use with just one ram stick.
You start the motherboard by a momentary short of the two PWR pins.
As to a new build,
A I3-12100 will cost something like $160.
It has twice the batch performance and twice the single thread performance as your current processor.
32gb of ddr4 ram will be about $100
A B660 motherboard is about $150.
Nowhere near $3000 today.