I am almost sure his problem is his cooler fan applying too much tension on his motherboard causing a short. I have a b450 f from Asus. Installed a ryzen 7 3700 using the boxed fan. It resulted in no dual channels and only dimm 1 and 2 to work. After a week of trial and error inclusive all bios tweaks possible to make that shit work. I even dismounted the AM4 foxconn socket to check the cpu pin sockets. Cleaned everything. 8bstalled my previous cooling tower for AM4 and ditched the boxed one aside. TADAAAAA ! BA DUM DISH !! DUAL CHANNEL WORKS and all other dimms too. I was so frustrated to the point to break my new mobo to find out what could be wrong.

Please do keep in mind not all rams support dual channel. You really have to look at the list provided by the motherboard vendor.