Couple of questions if I may:
Are the 24 pin and 8 pin power connections securely in place and the same for the 4 pin CPU cooling fan connection.
Is the build already inside of the case, if yes, see my canned text below;
Remove the MB and do a bare-bones set-up on a piece of cardboard (make sure it is larger than the MB) only connect the PSU, the screen to one of the MBs own video ports, 1 stick of Ram and the keyboard.
IF your MB doesn`t have a power test switch you will then need to short out the 2 power on pins on the MB header to get the PSU to activate, you can use a small flat bladed screwdriver or a paper clip bent into a U shape, this is perfectly safe if you do not touch anything else, the idea is to see if we can get a BIOS screen if you do you can then add one component at a time until you find the problem component, you must power down and remove the power cord from the wall before adding another component, second suggestion try a known working PSU, it is not unknown for new components to be bad.
Other things worth checking include, if you used stand offs beneath the MB are they in the correct locations (only where there is a screw hole in the MB) otherwise the MB will short out, check for stray screws or bared wires for the same reason, make sure the jumper cap that can be used for clearing the CMOS is not missing or on the wrong pins and finally try removing the CMOS battery for a few moments and then replace it, this will clear any possible bad MB settings.
To ensure that you receive notification of any reply to your thread click on the Follow this topic tab, top right corner above your OP.
Off to work now but will check back later.
BTW, if you have not got an onboard BIOS speaker I suggest that you purchase one, see my attached example;