It may be, this was in Chrome on an Android phone. Go to the inbox and it'd pop up app store. Close it, and the browser would be displaying the message about soon having to install messenger instead of inbox. Close that message and the process would repeat.

Only by visiting my friends profile and hitting the message link could I actually break out. It'd still take me to the app store but on close my friend's messages were visible along with the box to send a message.