Everything in pc is running but will not boot

[KLOmegalul]

In an attempt to upgrade my hardware from ddr3 to ddr4, my pc has ended up not working. Everything inside the pc would run just fine. RAM would have its rgb glow, gpu slotted in, power supply pins in, and sata cables attatched. Everything should be operating just fine, but my motherboard displays a small red light next to the word "BOOT". in the manual, this means the pc cannot find the boot device. This makes no sense as the sata cables are in just fine and all drives have their power too? Everything seems to be operating just fine but I still get this error no matter what I try

I'm at a bit of a loss but I need this PC fixed ASAP so I can meet my deadline, any help?

specs:
RTX 2070
AMD Ryzen 5 3600x
MSI MAG B550 Tomahawk wifi
Cooler Master Elite v3 600
1tb HDD
256gb SSD

[cm992]

Try booting with only the drive that you installed windows on. Try getting into bios by hitting delete key during boot and see if the drive is detected in the bios

[KLOmegalul]

No luck, same thing happens. Nothing happens when I input on the keyboard either it just remains a black screen with no signal