I have a late 2015 iMac now running High Sierra. I have latest version of iTunes. When I open BT Cloud and try to upload my music a box opens to tell me that no iTunes library is detected. I have ticked the "Share iTunes Library with other applications." box but nothing changes/no upload.
This problem has been apparent with all versions of Mac software on my computer (Sierra etc etc.)installed
Consequently I have used BT Cloud very little.
Also when I open BT Cloud the 'Transfer' icon has a little exclamation mark against it. When I click on 'Transfers' the whole BT Cloud program crashes and eventually a box appears asking me whether I want to report the issue to Apple.