common room laptop does not boot

[LukasFreeze]

This was all @reogaro could get out of the laptop in the common room Friday night:

It worked fine a few hours earlier when @Bjoho504 gave a large format printer introduction.

Restarting, also after taking the battery out for a moment, did not help.

[reogaro]

Yes. The following happened:

1. Introduction (using the laptop), no issues
2. Laptop was turned off and returned to the speakers' desk (By Bjoho504)
3. Grilling
4. I take the Laptop, go back to the large format printer, plug in the charger and mouse, turn it on on
5. "Bootable device was not found"

I tried rebooting a few times, with and without the charger, and poking around in the boot menu and BIOS a bit, no success. I suspect secure boot or boot partition issues, but did not investigate further.