iPad screen sharing

I can't connect my iPad to my MacBook Pro via cable.

I've never been able to connect wirelessly, and when I went to the Apple Store, they suggested I connect via USB-C cable. It worked fine for almost a year, but a couple of weeks ago, I was using my iPad as a second screen for my MacBook and it disconnected while I was using it. When I opened the Display preferences, my iPad was no longer listed as an option.

I've tried every cable I own - they all charge my iPad, and I'm able to use them for data transfer on other devices, so it's not the cable. I've checked all the settings, including making sure that both devices trust each other, and that screen sharing is enabled. I've restarted both devices many times. I'm just not sure where else to look for options.

Trying to go back to connecting wirelessly isn't currently an option, as I am at sea without wifi most of the time.

Could there be an issue with my MacBook?