This is a great question. For each User ID (which is your email address) the app allows you to have two (2) users logged into the app at any given time.
For example, if you are logged into the app with your iPhone and then you log into the app with your iPad, then you are at the maximum allowed logins.
Then say you login with a third device, you will receive the 2 User ID message. If you un-install the app without logging out first, (see below) you will also get this message.
The Vibes Music App has a LOG OUT button in the top right hand corner of the HOME screen. (See photo) You must logout of one of your devices before logging into another device.
The good news is that the Vibes Music App will not clear your downloaded albums if you log out!
One more thing: Many times when we have app issues, our first response is to delete the app and re-install it. However, with the Vibes Music App, you DO NOT want to delete the app unless you physically LOGOUT of the app first. If you un-install the app without logging out first, it will consider you as being logged into the app and you will not be able to install and sign in again. If this happens, please contact us at email@example.com and let us know what steps led to the login issue so that we can get you the technical support needed to log back in.