There's a way to do it, however, that change will always cause the users to lose other abilities like manual disconnect/reconnect. So, you need to use a feature called "location awareness" which can help auto-connecting/disconnecting based on certain creteria.
Location Awareness - https://docs.pulsesecure.net/WebHelp/PDC/9.0R1/Content/PDC_AdminGuide_9.0R1/Configuring_Location_Awa...
Connection set options - https://docs.pulsesecure.net/WebHelp/PDC/9.0R1/Content/PDC_AdminGuide_9.0R1/Pulse_Secure_Connection_...
Connection options:
- Allow user connections—Controls whether connections can be added by the user.
- Allow user to override connection policy—Allows a user to override the connection policy by manually connecting or disconnecting. Typically, you leave this option selected to make sure that a user can establish a connection under all conditions. If you disable this check box, the user cannot change the endpoint’s connection status, suspend/resume a connection to Pulse Connect Secure or shut down Pulse Secure client.
VPN admin UI Path - Users > Pulse Secure Client > Connections
