'Library Full' error message - but my storage is nearly empty!

[jamesroot92]

Plan

Premium

Country

UK

Device

Huawei P20 Pro

Operating System

Android

My Question or Issue

I keep on getting an error message saying that my 'library is full' and that I 'need to remove more music' to continue downloading songs for usage offline.

However, this is a brand new phone and there's no way that my memory is full. So I wonder, would there be an issue with having music saved on my old phone at all? I can't just delete the music on my old device as it was lost a few weeks ago. 

Is there a way to remotely remove all offline tracks across all my devices on my account? Thanks in advance for any responses