Teh AB code is, BIOS initalization, started but stops.
Need to do a basic test.
Wit the MB on it's empty box.
Turn off the PSU.
Remove the GPU, RAM is installed, any other cards, all connections except the following. Checking each one to make sure it is properly seated.
CPU and heatsink/fan, fan plug to CPU#1. (top left of the DIMM slots)
24 pin 24v main power and 8 pin 12v Auxiliary. (JPWR1~2: Power Connectors) page #36.)
Connect the peeper, ensure + positive is correct, (JFP2 page #38)
Turn on the PSU and short out pins 6 and 8 (JFP1 page #38.)
The PSU fan starts, (may stop if thermally controlled)
The CPU heatsink fan should start and keep going. and you should hear 3 short beeps, if not.
Overheating because no thermal paste, improper heatsink installation.
Faulty CPU or MB.
Bent pin/s in the MB socket.
Turn off the PSU, > install RAM in the correct slots, > test again,
Beep code may change, or, you may not hear any beeps, but if it keeps going.
Switch off the PSU.
Add, mouse/keyboard, connect monitor to the MB video port and test again.
If still OK, carry on with your build.