B1 and B2 slots not working.

Have you guys found any solution? I have same problem too

Hello everyone, I've got a B450 Asrock Fatal1ty Gaming K4, and after upgrading my CPU to a Ryzen 5 5600 which after trying absolutely everything I could think of to get it to work I just couldn't figure it out and ended up RMAing it and putting back my Ryzen 5 2600X but after that my B1 and B2 RAM slots stopped working suddenly.

Extra information :

Tried the B1 and B2 slots individually system won't post.

Using A2 and B2 the system will show both sticks on the BIOS but only 8gb out of 16 total ram (this is on both memtest86 and windows)

System was working fine on the BIOS version 5.60.

Things I've tried:

1. Reseating the CPU.
2. Less and more Mounting pressure
3. Checked the CPU for bent pins, couldn't spot any.
4. CMOs reset, putting the battery out for an hour.

But nothing works, a new Ryzen 5 5600 was sent from the store I sent the non functional one, so could the non working one have damaged something on the Mobo?