Spotify can't find my Android Phone, it doesn't show up in the Devices list and I can't sync my local MP3 playlists to it.

Both the PC and Spotify are on the same network. Both Spotifys are logged in to the same account and can access the internet and play music. Online-Playlists are synced to the phone immediately and I can download online music no problem. I just can't sync my local MP3 playlists to the phone because it doesn't show up in the list of devices.

I have this issue both at my home computer and my office computer on another network. It's never worked on my home computer, but it worked on the office computer until a few weeks ago. I had a few weeks of sick leave and when I came back that computer couldn't find the phone anymore either.

I tried reinstalling the app on the phone and on both computers. Firewalls are not blocking traffic and antivir is not interfering. My Spotify account is premium of course.

I'd really like for this to work again!