This issue has been already posted several times, but no solution up to now.
Some people have the problem of not having an Internet connection for months. Or at least, not good enough.
This can happen to military, fishermen or humanitarian aid workers. Spotify disables the downloaded music in case the App in the device does not go "online" at least once every 30 days, no matter if you pay the subscription or not.
Therefore, one can be paying the Premium subscription to Spotify, but not having the downloaded songs available due to a lack of Internet connection (it occurs even when there is Internet connection, but not "good enough" for Spotify).
So, my request to Spotify is to find a different way to have the downloaded songs available even if the App cannot go online.