If you are receiving the message,"Your Pandora Account is currently playing on another device,"or"Someone else is listening,"then more than one device is streaming from your account at the same time.
While your Pandora account can be logged into as many devices as you like, they can't be playing at the same time. Regardless of your subscription level, the revenue from one Pandora account only covers the cost of one stream from one device. As long as you press pause on one device before you listen to Pandora on another, you should be fine.
Unauthorized User on my account:
If you believe this error message is popping up due to an unauthorized user accessing your account, and would like help with disassociating or removing any devices that are logged into your account, please contact our support team for further assistance.
At this time, listeners cannot view or remove devices logged into their accounts manually.