New phone won't sync local files from pc

[Ryuunosenshi]

Plan

Premium

Country

Device

Samsung Galaxy Note9

Operating System

Android 8.1.0

My Question or Issue

 Since a couple of days I have my new phone and I've been trying to sync it to my computer so that I can play all my local files on mobile, however, nothing I do seems to work. 

I've done everything the same way I did when I synced local files to my previous phone (Galaxy 7Edge) but nothing so far works.

Things I've tried:

-re-instaling the mobile app

-having my phone and computer on the same wifi network (inclusing creating a mobile hotspot to which I then connect the pc, something that was always required with the previous phone)

-having the 'download' option checked in the playlists on mobile

-connecting the mobile to pc via usb cable

-having my pc recognize my new phone as another device (I can play and control spotify just fine on pc using my phone, just not the local files)

I'm really running out of options here, I really don't know what else I could do or if it's even possible to play local files on Note9/Android 8.1.0 in the first place.

Thanks in advance