Really not enough info to help. 1) Re-check that you properly reconnected your power connections to the motherboard: the 20 or 24-pin main cable and the 4 or 8-pin cpu power cable. Make sure the power cable connectors "clicked" when you pushed them in. 2) If you added any hardware, you may want to be sure your PSU has enough power to handle that hardware. 3) You may want to check that your PSU hasn't failed.
Thanks for your help. It appears to be a problem with the motherboard, according to their technical support. Every powers up when I plug in the server. SCSI controller lights up, fans run, CD-ROM opens and closes, microprocessor fans turn on, etc. So, I know I connected the power supply correctly. I have tried to unplug everything including the SCSI controller, CD-ROM, floppy disk, hard drives, etc. just to see if anything was causing an incompatibility issue but it still wouldn't boot up to at least the BIOS screen. I hope this extra information is helpful, but I fear it is the motherboard and I will just have to send it back.