New(ish) pc wont display

[BestReinInNA]

Finally decided to rebuild my old Alienware aurora r4.  New mobo, new cpu, new ssd, new ddr4 ram. Same old case, psu, gpu and monitors. When I power it on outside of the case the fans turn on but nothing displays, and Ive been going crazy. I tested the gpu on another bench and it runs fine. I tested the psu with a multimeter and all the voltages are normal. Everything appears to be seated right. Ive tested different hdmi cables and my other monitor. My friends who have built pc’s can’t figure it out. Hopefully its something simple that my friends and I have collectively missed, but any help is very appreciated. 
 

specs 

mobo: Asus pro b660m-c d4 csm

cpu: I3 12100f lga 1700

Memory: corsair vengeance 16gb (2x8)

storage: crucial p2 1tb m.2-2280

Gpu: gtx 550ti (not my main gpu for this build but Its the only one I could verify is fully functioning for troubleshooting)

Psu: dell n875ef-00 825 watts 

 
any help is appreciated 

[DarkD]

Something similar happened to me with an rx 570 and it wouldn't boot on h110/310/510 boards but runs perfectly on other boards because it was a weird brand from china. 

It's not logical just maybe just incompatibility between your card and board 

[BestReinInNA]

1 hour ago, DarkD said:

Something similar happened to me with an rx 570 and it wouldn't boot on h110/310/510 boards but runs perfectly on other boards because it was a weird brand from china. 

It's not logical just maybe just incompatibility between your card and board 

One buddy of mine did say that as well. Definitely one of the things Id have a hard time fixing without other gpu’s to test it.