If the app gives you an unexpected error, you might need to reinstall your ExpressVPN configuration.
To reinstall your connection configuration, tap the Options menu (≡) in ExpressVPN.
In the Options menu, 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.