It looks like your account is currently set up with the free service.
@rat688 The ability to listen to songs on demand is only an option when upgrading to Pandora Premium.
It looks like you enabled a complimentary session of Pandora Premium, which allows you to interact with an ad in order to listen to content on-demand.
Because these sessions are funded by advertisements, your account reverted back to your regular service automatically at the end of the session.
This would explain why you aren't able to play through all songs in your collection in succession - your account reverted back to the free service when the session was over.
Hope this helps explain!
... View more