Hardware

I have an old HP Z800 workstation. I've enabled the Compute for PCIe-16 slots and now it's not booting anymore. It beeps 6 times and pause then beep again. There is no LED light on the power button. Here's what I have done so far to troubleshoot this error and it still beeps 6 times.

1. reset CMOS by removing the battery
2. remove cards from all the slots
3. remove memory card and leave only two sticks in

I don't even get to the POST screen. It starts beeping right after I press the power button. I'm not sure what else to test. I've also posted this same issue on HP forum but not one seems to have an idea. This Z800 was working fine until I try to install a Samsung 970 EVO SSD 1TB - M.2 NVMe and it wasn't detecting it as a boot drive. However, now, I can't even boot the computer anymore. Any help is much appreciated.