Question replacement defect ASUS M5A97 R2.0 motherboard

[hartings]

I have issues with the SATA speed after 3 subsequent quick power outages. The SATA speed goes down to 1.5 from 6 Gb/sec. New disks and cables. Replaced cables. Same problem. Otherwise the motherboard works flawlessly (linux CENTOS 8). I bought two identical replacement boards which both do not start. The green light on the board goes on, but that's it, nothing else! All disks and fans are off. I replaced back an forth, but only the original board will start the fans and disks, also after I tested both replacement boards twice without success. I am sure I connected both replacement boards correctly. What am I missing? Or can it be that both replacement boards are defect?? Must be very unlikely.... what else can I do?
Any comment is appreciated.

 

[hartings]

Solved! My old motherboard was configured in the BIOS to restart on power outage, and my main power switch was broken. The new boards were not configured in the BIOS to restart on power outage and never received the power-on signal from my computer as the power switch was broken. It took some time and 2 other motherboards to realize this.....
Thanks for reading.