[Tonez]

Thanks for looking into this Mike. I have also been trying various things in the meantime.
The problem first emerged (I discovered late last night) with empty setlists, and collections. Unless one of these had a song assigned to it the lists wouldn't sync. Specifically, I created them on the PC but unless they were populated, they wouldn't appear on the Surface Pro. I don't know whether they failed to upload or download.
However, this morning I simply cannot reproduce the problem! I synced first thing this morning without making any changes at all and the empty setlists and collections did in fact transfer. <grrr>

I can now make changes on either machine and, following a library sync, they are reflected on the other - as I would expect.

If I can replicate the problem again I will update you.

Thanks for checking this out.
Oh... FWIW I did notice at one stage when the problem was happening, that the time stamps on the cloud sync folder were older than when I last sync'd - which seems to indicate the problem was with the upload from the PC.

just a thought...

Cheers
Tonez.