Since your playback works, it’s unlikely that this is an issue with Max2Play or your hardware. There have been some reports about certain ISPs in the US restricting Pandora use but that would also result in a hard error when trying to use it. Since your issue seems to just be an unrecognized premium status, this is most likely a problem on the end of Pandora or mysqueezebox.com.
Have you had contact with Pandora yet? If not, please try doing so and asking about your account and its limitation despite your premium status.
Pandora Tech Support