Fatal1ty AB350 Gaming-ITX/ac & 3700x

Hello, so my experience till now with this combo ... not good. Previously I used an 1600 with it and all was fine. So, long story short, my setup

Fatal1ty AB350 Gaming-ITX/ac bios 5.70 (ok with 1600) - > (switched the cpu to 3700x)
The VRM heatsink was replaced with the one with more metal than termal foam.
Ryzen 5 1600 -> Ryzen 7 3700x
2x8 GB G.Skill FlareX
512 GB nvme Samsung 950 pro with heatsink
Win 10 pro
Case Node 202
Cooler Noctua NF-9a
So I updated the bios to 5.70 while the 1600 was still on it as per instructions, and replaced the cpu to 3700x. First boot was all ok , the

temps started to go a bit high in 70 C but not reaching 80, this just in windows, so I assumed it is fine, the cooler setting was on standard so

I just wanted to change it to performance once the new bios 6.0 was flashed.
But as a precaution once in bios ( still 5.70) I changed the fan level to performance and rebooted. And from here it went into a boot loop, the

first time the memory was still on XMP so it could not be in "retraining" as it worked fine on first boot.
So I let it boot loop 4-5 times, till once it stopped and it did not start at all. I started it again from button, it did 3-4 loops never

reaching windows and stopped again.
Third time it did nothing ... did not start at all.
By the way this was with the case opened. When I disconnected the cables and checked all case, cooler, mobo were extremly hot, vrm heatsink all.

Since then it did not made it run. I left it to cool down, put back the 1600 but still the same, not a peep. May be you can offer some guidance

regarding how can I check if it is really fried. tried to clear cmos, removed the battery pin, still does nothing.

Best regards,
Gmt