At the forefront of many memory issues is a well known tenet of the builder and enthusiast community that while mixed memory (Memory modules that did not come together in one kit, regardless of whether or not they have the same part number or have similar specifications) certainly CAN work together in some cases, OFTEN it simply will not. Right up front I'll tell you that if you are trying to get sticks to work in the same machine together that were purchased separately, even if they are otherwise identical according to the kit or model number or if they would seem to have identical timings and voltage requirements, there is STILL always a very good chance that they simply will not work when used together.
(There is also a good chance that you MIGHT be able to get them to run together IF you are willing to not be impatient, listen to and understand what it is you need to do and follow the steps necessary to determining if they will "play nice" or not.)
A word of advice. If you just purchased this memory, and for whatever reason you bought two separate sticks of the same memory instead of buying them together in a matched set, see if you can return them for a refund or credit towards buying a similar or same set of matched sticks that come together in a kit.
It is ALWAYS better to have matched modules because from brand to brand, or even within the same brand, in fact, even when the part numbers are IDENTICAL, there can be anything from simply slightly different memory chips that were sourced from different bins at the end or beginning of a production run to entirely different configurations altogether even though the model numbers seem to be the same.
So, in essence, they might or they might not work together. You can try, but it's a hassle to deal with returns. You'd be much better off buying one matched set that uses 2 x however much capacity you want to use, and then sell the other sticks.
There is a more in depth guide about this here:
*Resolving memory problems and setting up XMP/DOCP/AMP profiles
Facebook
Twitter
Instagram