Where exactly did you set your Spotify username and password? Do the files have the correct permission for the user that Mopidy runs at? Have you read https://docs.mopidy.com/en/latest/debian/#differences-when-running-as-a-system-service ?
Where exactly did you set your Spotify username and password? Do the files have the correct permission for the user that Mopidy runs at? Have you read https://docs.mopidy.com/en/latest/debian/#differences-when-running-as-a-system-service ?