You can sign into the OverDrive app on up to six different devices (Android, Fire tablets, Chromebook, iOS, or Windows 8/10) at a time using an OverDrive account, Facebook, or your library card. This also authorizes the device to download Adobe (DRM-protected) ebooks and allows you to sync your progress and bookmarks between devices. Visit this help article for help managing saved devices.
You can also use an Adobe ID to sign into up to six devices at a time. If you've reached the activation limit for your account, contact Adobe Customer Service and ask them to reset your Adobe ID.