It may sometimes be that you can't connect to a desired server. Usually selecting a different server solves this problem.
Options you can also try in the app:
- Disable the 'Smart server/Automatically use the best server' option in the server list/settings.
- Change the protocol, you can set this in the settings.
- Log in again in the app.
- Reinstall the application once. This is best done by first uninstalling the application, then restarting your device and then doing a new download and installation of the application.
Does the VPN connection still not work? Please send an email to email@example.com.