Why can macOS users not connect to our office L2TP VPN over IPsec (Draytek Vigor 2952) using the built-in Mac VPN functionality but Windows users can?

Hi all, I am have set up user accounts for both Windows and Mac users for our Draytek VPN and put in the exact same pre-shared key and IP address - but Mac users are unable to connect using these credentials using the System Preferences > Network menu.

The error message I receive is 'The L2TP-VPN server did not respond. Try reconnecting. If the problem continues, verify your settings and contact your administrator'.

Can anyone help? As far as I can see all the settings are correct.