If the app gives you an unexpected error, you may need to reinstall your ExpressVPN configuration.
Tap Settings > Reinstall VPN Configuration.
A notification will pop up. Tap Allow.
The app will notify you: ‘ “ExpressVPN” Would Like to Add VPN Configurations.’ Tap Allow to continue.
Use your Touch ID or enter your passcode to add the VPN configurations.
Your VPN configuration will be reinstalled now.