In Google Play, the bell icon next to the search box was saying I have 1 unread notification. However, when I tap the icon, there are no notifications listed, and nothing in the “Offers” tab either.
I tried force stopping the app, clearing the cache and restarting, as well as restarting my phone, but neither made any difference.
After speaking to Google support, the “solution” turned out to be uninstalling all Google Play app updates. This got rid of the phantom notifications, even after Google Play was updated to the latest version.