The ram should be in A1 and A2, or in B1 and B2, showing to be 1st and 2nd to the left from the CPU, or in 3rd and 4th to the left from the CPU in order to run in dual channel. It should work in A1/B1, maybe A2/B2 but not in dual channel. Any combo of A1/B2, A2/B2, or A2/B1 probably won't post.
If you've tried the ram individually in A1 only, or in B1 only verifying that both sticks do 100% work, but none of the above dual channel configs work, then I would RMA the motherboard or try to get Micro Center to warranty their labor and make them RMA it.
Individual slots can be faulty. I refurb OEMs/random parts I scoop up into budget gaming comps and flip them as a side business and recently I had a Compaq motherboard with a dead A2. It would post B1/B2 dual channel or A1/B1 non dual channel, but anything in A2 at all and no post.