Hi and welcome to TSG.
Please post a list of the parts you used for the new build, exact motherboard, cpu, ram and graphics card.
Also was the old PC a big brand type like Dell, HP etc ?
Are you using the same case for the new PC that was used for the old PC ?
What PSU do you have in the new PC ?
Check that the ram is fully inserted into the slots, the catches at the end of the slots should snap into place.
Ensure the stand-offs in the case are all under screw holes in the motherboard.
Make sure you connected all the required power leads to the motherboard and graphics card.
If the motherboard has graphics connector(s) make sure you connected the monitor to the graphics card.
Please post a list of the parts you used for the new build, exact motherboard, cpu, ram and graphics card.
Also was the old PC a big brand type like Dell, HP etc ?
Are you using the same case for the new PC that was used for the old PC ?
What PSU do you have in the new PC ?
Check that the ram is fully inserted into the slots, the catches at the end of the slots should snap into place.
Ensure the stand-offs in the case are all under screw holes in the motherboard.
Make sure you connected all the required power leads to the motherboard and graphics card.
If the motherboard has graphics connector(s) make sure you connected the monitor to the graphics card.