Hi, welcome to justanswer.com! My name is Mike.
I will need some information before we begin:
Please go to the Apple on your computer in the upper left of your computer screen to About This Mac and give me this information:The exact system Version (listed right under OS X ??)ProcessorMemory
That depends are you a member of Apple Music or Music Match are you using the iCLoud Music Lbray, etc... I can help you by remote on this