Z790-H Blinking Red CPU Light No Boot

[usernomad]

Z790-H  *  i5-13600K  *  32GB Vengeance DDR5 6400  *  WD_BLACK SN850X NVMe 2TB (X2)  *  RTX 4070Ti  *  MSI MPG A1000 PS

I've been running this system for 2 months with no issues. It's been great. Today I turn it on and it will not boot, monitor does not receive a signal, the red CPU LED blinks on and off every second or so, and the PC fans speed up and slow down over and over. 

I would appreciate any help on this. My trouble shooting knowledge is limited. I build a PC every 7-8 years or so and only learn enough to pick the right parts and put them together. I rarely have issues so I'm inexperienced with fixing problems. I've searched online for possible issues that would cause this and depending on where I look it seems like it could be one of ten different things. If someone could give me a list of steps to try, or point me to a reliable resource, or whatever, I just don't know. I need to get this fixed ASAP, so any help would be greatly appreciated. This was unexpected. I literally just repaired my clothes drier, put it back together, came in and turned my PC on and it does this. Thank you ASUS community. If there are any questions just let me know.

[JohnAb]

Difficult to give any helpful advice, but I think I'd start by double checking all connections between the motherboard and PSU, the GPU etc. 

Based on the history you describe, I'm wondering if the PSU might have developed a fault. Either that of maybe a poor connection. Has the PC been moved or knocked? Are all of your front panel switches etc also properly connected? 

Also, just have a look in the motherboard manual to see if a flashing red LED has any particular meaning. I'm pretty sure that my motherboard doesn't have any flashing lights normally.