Synchronizing - unknown error -54
I have tried to synchronise between my iMac and iPad - for the first time ever, I can't. It gives an error message that it can't write to Mactintosh HD, unknown error (-54).
I have the latest iTunes software and run macOS Sierra. I have restarted both iMac and iPad 2 but with no luck.
The only new thing is a new cable; could this be an issue (not an Apple but a Belkin)? I have previously bought a cheaper cable, however, it wasn't compatible. It seems to work and start synchronising but stops in the middle. I saw a thread that I should ctrl + click on the iPad icon, but I couldn't make that work.
Can anyone help?
iPad 2 Wi-Fi + 3G, iOS 9.3.5