When Diagnosing Boot issues, You need to verify some basic stuff is working. Plus, Its a good idea to remove the components from the case and place on an antistatic work pad, or Bench mount.
I would start by Removing all the components. Disassemble the primary components.
Setup your system in this configuration first.
Powersupply - Test your psu. On another compatible system if necessary, a PSU tester is recommended, although they cannot provide load testing.
Motherboard - Reinstall the CPU, Take it out, Examine the Socket, look for bent pins or debris.
CPU - Examine the CPU, check for lack of indentations on the surface of the CPU, this may indicate the CPU is not Docking with the Motherboard correctly. If installed correctly, you should see a sign of Pin-to-surface contact. Reinstall the CPU, don't be hasty. Make sure your Motherboard is as Horizontal as possible, be careful not to load the cpu compression plate to quickly. Install the HSF (Heat Sink/Fan) Assembly with a small amount of thermal compound. Spread evenly Hotspots=bad.
Connect the 24PIN Main connector and the 8Pin Aux Power Connector. Connect you Power cable to the PSU. Connect a Speaker to the Appropriate Header Pins so you can hear error beeps.
Identify with your Motherboard manual which 2 Pins on your Pin Header are the Power Switch, then close the gap with a metal filament or connect the Switch from you PC Case and Trigger the Motherboard to start. You should get some kind of beep error. That is ok, it is expected. This verifies that the basic system is performing diagnostics which we need it to do. Note the Beep codes and reference the manual, the first code should be Ram not found. Power the system off.
Next connect your Monitor cable, and Install your RAM into the Slots Labeled DIMM_A1 and DIMM_B1.
Power the System back on. If your system post's, GG your Good to go. If it gives you an error message, refer to the manual for error codes and reply here accordingly.
If your system Will not Power on after your First power attempt, Disconnect the Power Supply, Remove the CMOS battery, and go have a coffee. Take about 5 minutes, it will be the longest five minutes ever, but your system needs time to clear. Don't rely on the CMOS clear for this proceedure.
Replace the CMOS Battery, Connect the Power Supply and Trigger the Motherboard again.