Unable to connect my iCloud Music Library to my Iphone SE

Hello,

I bought an Iphone SE from a friend and I connected my Apple ID to it and everything works perfectly. Anything but my Apple Music library: I can't open it on this Iphone. When I go to Settings > Music, I can switch on 'Show Apple Music', but if I try to switch on 'icloud Music Library', I get the following notification: 'iCloud Music Library can't be turned on because this device is already associated with another Apple ID. This device can be associated with another Apple ID in 90 days.'

What's strange, is that the device is connected to my Apple ID (the same Apple ID that is connected to my Itunes/Apple music account), and the previous owner of the device has disconnected it from all possible Aplle ID's or Itunes accounts.

I already tried to log out and log in again, to disconnect and connect it again from my Macbook. What more can I try? Any help is very much appreciated! Thanks.