More than happy to give this a go, but how do I boot it in safe mode if I can’t see what I’m doing on the monitor?Hello Joannec. You mentioned that you see the error "input not supported" on your monitor. That may suggest that the screen resolution was set to a high resolution not supported by the monitor. Do you know if anyone attempted changed the screen resolution?
You can try booting the PC in safe mode, which will use a low screen resolution, and the monitor should then work, and allow you to change the screen resolution permanently to one supported by the monitor.