Question Computer fans spin for a sec before turning off

[Shorts1113]

Mobo: Asrock b250m pro 4
Cpu: intel i5 something
Gpu: nvidia gtx 1660
RAM: 16GB Gskills
PSU: 550W

basically the title. Moved a perfectly working PC into a new case. When powered the fans all spin and lights come on for a second but then turn off pretty soon after. Monitors receive no input.We have checked header pin connections, Ram connection, mobo power, cpu power… anyone have any suggestions?

 

[Lafong]

What happens if everything is placed on a table outside the case?

 

[Shorts1113]

Mobo: Asrock b250m pro 4
Cpu: intel i5 something
Gpu: nvidia gtx 1660
RAM: 16GB Gskills
PSU: 550W

basically the title. Moved a perfectly working PC into a new case. When powered the fans all spin and lights come on for a second but then turn off pretty soon after. Monitors receive no input.We have checked header pin connections, Ram connection, mobo power, cpu power… anyone have any suggestions?

Update: After placing RAM in a different DIMM slot everything seemed to work fine. Now trying to fiddle around with getting it to output to monitors but should work fine