I think you have the wrong processor installed. The i5-3570 is a 3rd Gen CPU while the 7020s take 4th Gen CPUs. The K variants do not work in the SFFs - only in the MTs (with modifications.) The best CPU for the 7020 is an i7-4790, or an i5-4690, if you wish to keep it as an i5.
I put an intel i5-3570k inside my 7020 and I now can't boot it the amber light turns off and on so I need a better power supply can someone give me a solution?
OptiPlex 7020 SFF, power supply fail?