My Edge 1040 will not start. It keeps looping at start up but goes no further

When powering up, the Garmin logo appears and then it disappears, before looping and trying to boot up over and over again.

I have tried to reset with 30 second power button but no success, except I sometimes see a black line across the screen before disappearing.

I have tried to reset pressing start and lap + power, before releasing power.

I have managed to access the USB mode to connect to Garmin Express, while it allows me to see my files on my PC, it doesn't help me diagnose or solve the problem.

Help please.