@Timo - Ouch - sorry to hear that.
I'm also using the Noctua cooler (U14S TR4-SP3) too... This is a mobo /cpu from China, bought of ebay for a great price,.. but here I am.
In *frustration* I (somewhat gently) played with the cooler, wiggling it,.. trying to apply a bit of pressure to the cpu board,..just to see what happens...
Guess what - it just booted and the power LED came on...LOL! So,.. I'm thinking... this cooler... in a tower,.. maybe these SP3 sockets are sensitive enough that the weight is enough..? I've had the board now for 4 weeks... Out of box it was fine,.. setup & running same day.. Ran till 4 days ago then I had this issue... Tried everything.. Only thing left to do was re-seat CPU but no tools.... I guess I'm gonna get the right tools and re-seat this ,...and a new cooler?
I really hope this is the problem.... I had such high hopes for a "Supermicro" board,.. but then again,.. these Epyc CPUs are just too big/delicate for their own good. Who knows,.. I will post again after re-seat etc. As previous poster mentioned,.. so many power related pins on these,.. and so many contacts.... Not great for confidence in a home lab server though....