Win 10 - 16GB DDR3 showing up as 8GB, then later 4GB?

[MaximumSquid]

Machine is 5 years old:
Was originally Win7 /w 2 sticks of DDR3 - 8gig
The Mobo:
https://www.newegg.com/Product/Product.aspx?Item=N82E16813128538

Is now a Win10 /w SSD. . .
My old RAM was suspected to be corrupt
Buying new RAM was cheaper than having the tech run a diagnostic

I bought a single 16GB stick of used DDR3 Ram; tested fine at the PC shop

A month later my machine read that it only had 8GB. . .
Didn't think anything of it at the time since I didn't need more than 8

Months later I check it again and it's reading 4GB

Same PC Shop, but different guy couldn't help me
He only had 2x sticks of 2GB DDR3 available to test with
&
Didn't have a machine to plug in my 16GB stick to see if it would read differently

Bios, Resource Monitor, and System all say I have a 4GB stick installed
MSConfig > Advanced Options does not have the Maximum Memory check mark ticked

I feel like I need to do more testing. . .
or
Should I just buy two new sticks of DDR3 and hope it works?

3rd option is to take it to another PC shop and try to confirm before buying

 

[GhislainG]

That motherboard doesn't support 16GB modules; you should buy a compatible 2x8GB DDR3 kit.

 

[USAFRet]

http://www.gigabyte.us/Motherboard/GA-Z68AP-D3-rev-20#sp

"4 x 1.5V DDR3 DIMM sockets supporting up to 32 GB of system memory"
So, 8GB RAM sticks. Not 16GB sticks.

 

[MaximumSquid]

How do I mark this post as answered?

 

[USAFRet]

How do I mark this post as answered?

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I've changed it to a Question thread. The Solution button should now appear for you.