cpu and vga fans spinning, no post, black screen

Hello ,so I've got the following issue, I've downgraded an Asrock AB350 Fatal1ty itx from 6.50 to 5.30 according to this video https://www.youtube.com/watch?v=ZzqwjVDKAnU&list=FLWf5ZXCVyoEnt6nf-36fJuQ , all went by the book, no errors, restarted into bios afterwards, 5.30 was there, the background also red, not black as in 6.x versions, changed the XMP and restarted, booted into windows, did various stuff from windows update to 2004 version, a little gaming, temps were fine, only thing I have noticed was that my previous saved profiles were still there, which I assumed will be deleted at bios update. Still after several hours I have shutdown the PC. Next day at start cpu, vga fans are spinning but no post , black screen , monitor shows no signal for hdmi. Tried all I could think of, changed hdmi cable, reset cmos, removed battery, still the same, I am kinda out of ideas and I do not have other system to swap components. It is strange how it was working for a full day almost and after an overnight stop does not work anymore.

So the specs are as follows:
Asrock AB350 Fatal1ty Itx
16 GB Gskill FlareX 3200 cas 14
Ryzen 1600
Gigabyte nVidia Windforce 1060 6GB
Corsair 600W PSU

Any ideas are welcomed.

Thank you, but it made no difference, just tried it. I have to fins another mobo, cpu and vga card to test my components and the mobo itself.

:-(, one mem stick I have already tried it, one by one in each dimm slot , also I am booting just with the hdmi and power cable, still no joy.

Yes :-)

Yes, well good intentions ... I wanted to do something similar but with a gaming cpu as it will be mainly used for gaming, so I've bought the 3300x, this is why I have upgraded the bios, the problem is that in the Node202 that cpu is very hot with the box stealth cooler and the nh-9La, in gaming was reaching 85-90C after one hour or so.I have reseated the cpu cooler several times, with no luck, the only acceptable temps were with the case open on the table. So the other option was to buy another cooler, like cryorig c7 or alpenfön black ridge, more money for an uncertain result. As the 1st gen Ryzen 1600 is "not recommended" to be run with the latest bios I've decided to downgrade and after some search I reached to that video. The rest you know. Thank you for the advice and stay safe.