Question New Build...no post.

[Disco_Billy]

So, I figured building a new PC would be fine even though I took about 15 years in between builds. And now I'm stumped. I can't get the unit to post or do anything at all.
I am using the following parts:

Phanteks P400a case
Corsair RM850x PSU
MSI Pro B760M-A
Intel I5
AMD Radeon 6600xt
I5-12600K LGA1700
Corsair Vengeance LPX DDR4 2x8 3200

I already replaced the new PSU with another one because I did the pin test and couldn't get the PSU fan to spin.
I repeated the pin test on the new replacement and the fan spun for a couple of seconds then stopped.
I plugged everything in as far as I can tell. The only items I connected to the PSU were the CPU, SATA, PCIe and the main motherboard (ATX/12V).
Phanteks included fans are connected to two sysfan connections, with the third connected to the pump fan connector since I couldn't find any other sysfan connections on the mb.
I installed the CPU, drives, ram, etc. without issue. Made sure the connectors were seated correctly.

I feel like I am missing something very simple but it's eluding me completely.

 

[rgd1101]

exact model of the i5?
ram?

 

[Disco_Billy]

exact model of the i5?
ram?

Thanks..apologies. I edited my OP to include the info.

 

[--SID--]

Remove the GPU and test with the monitor connected to the motherboard.

 

[Disco_Billy]

Remove the GPU and test with the monitor connected to th

I completely removed the card and plugged the monitor into the DP of the MB. Still, no power to anything that I can tell. I pulled the PSU connectors to the MB and reseated them too. These pics were before I pulled the GPU.

 

[Disco_Billy]

So, strangely, I pulled the case reset button header out and now the PC boots into the BIOS. I was waiting for POST beeps, but I guess I'm old and they're obsolete. The little LEDs on the motherboard went to green so hopefully all is well. I don't have a reset button so I guess it's no loss, but it seems weird that it would be the fix.

 

[geofelt]

Look very carefully at the front panel I/O header.
Orient yourself by looking for the open pins.
If, for example you connected the reset lead by mistake to one of the led pins you will get strange results.

 

[Disco_Billy]

I triple checked where I had placed everything and looked at the diagram provided by phantecs which showed where to place the leads based on the one missing pin on the header. Everything is running great now. Since there's no reset button, do I even need the reset switch? Thx

 

[geofelt]

I triple checked where I had placed everything and looked at the diagram provided by phantecs which showed where to place the leads based on the one missing pin on the header. Everything is running great now. Since there's no reset button, do I even need the reset switch? Thx

No, a reset button is mostly useless; leave it disconnected.

 

[Disco_Billy]

Ok, thanks.