Changed bios settings on old computer and now can't access bios or anything else

This one is a little bit strange.

So I've been toying with an old minipc I got from the tech people at work. Nothing serious, it's basically ewaste I've been trying to get to work with Home Assistant and the like. Part of the setup for that process was ensuring UEFI was enabled and disabling secure boot. So I did that, restarted the system, and now...

I can't get into bios.

Or the OS.

I can't get *anything* out of this thing. I plug it into my monitor, plug in the power cable, and all I get is a black screen. No signal. It's got power--the fan spins up, the light turns on, and if I wait a bit I get a quick two beeps from the built in speaker. I'm only partially sure I understand what that beep code means--it's an old Lenovo minipc from 2012, and I can't find great documentation for it (I'm 80% sure [it's this model](https://www.hardware-corner.net/desktop-models/Lenovo-ThinkCentre-M72e-Tiny/), however)

Obviously, not being able to access the bios or do. Anything. With the system has made it rather difficult to troubleshoot. I've tried plugging in various bootable disks--Ubuntu on a usb drive and a 3.5 inch ssd--but no luck. I also tried replacing the cmos battery--which is probably/possibly part of the beep code? (Either that or it's saying there's no operating system, but, well, see above).

If anyone here has any idea as to what I could do to get this thing running again, I'd be greatly appreciative. If I can just get to the point where I can do things with the bios again, I can possibly figure out how to fix any issues from there, but until then...

Well. If all else fails I guess I can use it as a doorstop.