This error is typically caused by a communication issue between Adobe and your mobile device. To fix the issue, follow these steps:
- From your home screen, go to Settings > General > Date & Time.
- Turn "24-Hour Time" ON.
- Power your iOS device off, wait a few seconds, then turn it back on.
- Open the OverDrive app. Deauthorize your device (from the Settings menu), then authorize it again.
Once you've successfully authorized your device, you can turn "24-Hour Time" OFF if you prefer.