Two RAM slots on the left side of my mobo stopped working | Please help me out

[zPrimZy]

So after 2 months of programs closing by themselves and random blue screens all the time I decided to just reinstall windows. During installation it blue screened, after that on start up no boot just kept beeping. I looked at the manual an it said for those 3 beeps it was a "Memory error". I took out all my ram out an tested them in every slot,They all worked in the last two SLOTS on the right side of the board. Every time I put all 4 of the ram sticks into any of the left two slots it just beeps. I don't know if they just died or need to be cleaned out. What do I do?

https://imgur.com/a/eDivN6t

MOBO: DZ77SL-50K
MEMORY: 4X2 8GB | an a 2X2 | making it a total of 12gb Ram
CPU: 3570K 4.4ghz | Hyper 212 EVO
GPU: 1050TI +160Core +550 Memory
STORAGE: 500GB SSD | 1TB HDD

 

[SkyNetRising]

Don't make multiple topics about the same issue. They will get merged together.

http://www.tomshardware.co.uk/answers/id-3808600/ram-slots-mobo-stopped-working.html

 

[Calvin7]

4X2 8GB | an a 2X2 | making it a total of 12gb Ram

Such combinations are not guaranteed to be compatible together. Problem may be your choice of memory.

Best memory performance always install memory in the blue DIMM sockets if
installing only two DIMMs on your board.

"last two SLOTS on the right side of the board" is not a recommended placement of memory.