If the power button is white, 1-2-3 LEDs indicate "routine system activity subsequent to video initialization"
Basically, that there is no video output. Do you have another video card you can try?
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I have same issue, but with T5610, I changed video card, still not works, I will try to find third video card to have a try, but I suspect it is not a video card problem.
Before I have this problem, I changed RAID mode to AHCI mode and do a power cycle.