What does that mean exactly and what do I have to do?
He tries to start over a network. Should he? If it's not a work laptop managed by your employer, probably not. Go into the BIOS, see how the startup sequence was set and change it if necessary.
The PC tries to boot from / over the network, which does not work.
Either the boot sequence is set incorrectly in the BIOS / UEFI, or your boot medium or the cable to it is defective.