Since what you get, are two sets of 2x RAM sticks, there is a 50:50 chance that all 4 DIMMs work together. And chance drops if both sets aren't same same make and model either.
Here's further reading about it:
https://forums.tomshardware.com/faq...y-ram-and-xmp-profile-configurations.3398926/
Now, i have done the same thing and i was lucky, that my two RAM sets worked together. Then again, i did all i could prior to that, including:
- Making sure from MoBo memory QVL list, that this specific RAM is supported in all 4 RAM slots at their rated speeds (3000 Mhz).
- I bought identical set to what i already had.
Regarding your case, and if you want a guarantee that 4x RAM sticks will work, buy a set of 4x RAM sticks.
Oh, you could try switching the RAM around, by taking the old set from slots A and putting them into slots B, while new set from slots B to slots A. It may or may not work. Other than that, there's nothing else you could do, besides buying a set of 4x RAM sticks.