We are currently aware that the latest Microsoft Windows Update - KB5009543 - is causing issues in the L2TP VPN connectivity. If you upgrade Microsoft Windows to this version at this stage, users of Client VPN will hit error 789 and fail to connect.
Our recommendation at this stage is to not apply the update, or if you have already installed it, to remove it as a temporary workaround.
We are investigating for possible solutions on our side as well, but this may require Microsoft's intervention.
We will continue to update this thread as we get more information on the issue.