While Connected to the VPN certain conditions of the internet connection can cause the S drive to show in offline mode
Please follow these Instructions to force online access :-
1 With vpn connected double click S drive to open
2 Click the home tab top left
3 Look for easy access then click on the down arrow then select the option work offline
4 Wait a few seconds then close the window then see if you can access s drive
5 Restart laptop and retry above if still not working