|Could be any number of things. You didn't provide enough information. List all hardware including PSU (power supply).|
Don't you have a manual? It should explain the RAM installation.
You should bench test a new motherboard with minimal hardware before installing in case.
A common issue is installing a standoff in the wrong place and shorting out the board.
Do you have all the power connections made. Two to motherboard and possibly one to graphics card. CPU fan connected to the correct header.