LMS can't save playlists - windows permissions required?

Hello.

I can't save playlists from Logitech Media Server. When I do it reports:

'Failed to save play queue!'

I assume it's a permission issue. My music and server is held on a dedicated Windows 10 machine. Can anyone let me know what permissions I need to set up on my Playlists directory ('write' I'm guessing) and for what (a particular user?)?

Thanks.