Spotify wont accept my username and password again

Yes, Volumio 2 is no longer mantained and so do its plugins.

Volumio 3 is fully stable as of now, and I think you will find the overall experience much better than 2.

To not loose your playlists I sugest you to subscribe to MyVolumio (the trial will do) before upgrading, this way you will find your playlists after the update thanks to the cloud backup.