If the VPN authentication window is constantly popping up on your screen, go to System Preferences -> Network and select the NordLayer connection. Make sure that Connect on Demand is disabled, then click Cancel and it should not re-appear.
If you are still seeing the popup, restart your Mac and drag the NordLayer app to the trash. Once that is done, re-install NordLayer application directly from the AppStore.
Note: In case you have any questions or are experiencing any issues, please feel free to contact our 24/7 customer support team.