Don't select your own answer as the BA in the future. Glad you got it sorted. In the future, keep in mind that the A2 and B2 slots are ALWAYS the slots the memory should be installed in IF:
It is a dual channel consumer motherboard.
You are using only two DIMMs.
Even if the board manual calls the slots something else, they will still be the second and fourth slots, for all four DIMM slot dual channel motherboards.