XPS 8700, no post, power button white

Hello, I have an old Dell XPS 8700 that I am having issues with. When I turn the computer on, the power button stays lit white the whole time, the motherboard has an amber light and the light for the power supply stays a solid green. The CPU,GPU and exhaust fan all turn on and you can hear the hard drive start to spin when first powered on. Issue is a black screen on the monitor with no access to bios either. I have tried a few things such as resetting and replacing the CMOS battery. I have also redone most of the connections from the PSU and finally I removed the ram and booted the computer to make sure the motherboard would send an error beep which it did. Another thing is when I power it on my mouse will not show any color. At this point I would think its an issue with the power supply I just don't have a spare one to test it and wanted some advice. Just ironic because I had no issues with this computer in the past and let it sit untouched for a few months and now have these issues. Thanks for the help!