Broken RAM slots?!

Oct 14, 2018
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Hello guys.
So today I cleaned up my motherboard, the CPU cooler and some dust on the mobo but I took off the RAM memory from the slots. After puttin back the motherboard, CPU cooler and RAM I couldn't boot, black screen and I can only hear some beeps from the mobo. I've got only 2 slots and 2 ram cards so I tried both of them in both of the slots one by one and I still didn't solve anything. :( Searched for some information and someone said it could be the cooler's backplate but it is not touching the case. I really don't know how to solve this problem as both slots "are not working". I couldn't have breaking them. Your help would be great!
Regards, Vlad.