iMac will not startup, all Internet Recovery options failing

Hi - My iMac suddenly will not start, and is showing the crossed through circle.

I have tried Internet Recovery on it but each of the options seems to fail.

Disk Utility seemed to run and instantly say there was no problem.

Restore from Time Capsule would not work saying there were no backups. (I have looked at the disk on another iMac and it's got plenty of backups).

Reinstall MacOS seems to go nowhere. On pressing the Continue button there is a message to click another Continue button for Apple to check eligibility. Clicking that just goes straight back to the main Continue screen.

And when I went to go for a Restart, a window came up showing no disk at all.

Any ideas welcome!!!