Mobo recognizes 2 sticks of ram, only uses 1

Solution
When all else fails read the manual on how memory should be populated in the four Dimm slots of the board.

1.If you want to install two memory modules, for optimal compatibility
and reliability, it is recommended to install them in the slots: DDR3_
A1 and DDR3_B1, or DDR3_A2 and DDR3_B2.

2. If only one memory module or three memory modules are installed
in the DDR3 DIMM slots on this motherboard, it is unable to activate
Dual Channel Memory Technology. Oopsy look where yours are installed.

3. If a pair of memory modules is NOT installed in the same Dual
Channel, for example, installing a pair of memory modules in
DDR3_A1 and DDR3_A2, it is unable to activate Dual Channel
Memory Technology. Two 8gb memory sticks dual channel mode.

4...

SaintAndrew921

Honorable
Jan 3, 2016
9
0
10,510
Having just bought an ASRock motherboard, I noticed in the manual that it says to use A2 and B2 slots as a priority. I know you said you've put the sticks in different slots, but I noticed that the current setup is B1 and B2.
 
When all else fails read the manual on how memory should be populated in the four Dimm slots of the board.

1.If you want to install two memory modules, for optimal compatibility
and reliability, it is recommended to install them in the slots: DDR3_
A1 and DDR3_B1, or DDR3_A2 and DDR3_B2.

2. If only one memory module or three memory modules are installed
in the DDR3 DIMM slots on this motherboard, it is unable to activate
Dual Channel Memory Technology. Oopsy look where yours are installed.

3. If a pair of memory modules is NOT installed in the same Dual
Channel, for example, installing a pair of memory modules in
DDR3_A1 and DDR3_A2, it is unable to activate Dual Channel
Memory Technology. Two 8gb memory sticks dual channel mode.

4. It is not allowed to install a DDR or DDR2 memory module into
DDR3 slot; otherwise, this motherboard and DIMM may be damaged.

5. Some DDR3 1GB double-sided DIMMs with 16 chips may not work
on this motherboard. It is not recommended to install them on this
motherboard.

6. For optimal compatibility and stability while overclocking memory
frequency, it is recommended to install one memory module on
DDR3_B2 slot or two memory modules on DDR3_A2 and DDR3_
B2 slots.

You should always read a motherboard manual from start to Finnish.
Sadly for most it`s read half way and thrown in a corner of the room, leading to the whole problem of headaches people have.
 
Solution

StrangeInstance

Honorable
Sep 23, 2012
367
0
10,790


Edit: sorry I said the wrong person answered it. Thank you regardless.



I gave that a go. It worked! Thank you very much.