Once VPN connects, the connection to the server drops.

We have several hosted environments, each hosted by a different managed service partners.

We use the FortiClient from MSP#1 on a server hosted by MSP#2 to send email.

Up until a month ago, the client/connection was working just fine. Now when the VPN connects, it no longer allows any network access to the server.  No firewall updates/changes have been made in our hosted environment from MSP#2. MSP#1 is saying that it's my issue not theirs. 

At this point, I am just looking for clarification on what would cause this to happen.  I would also like to add that I do not have physical or remote access to either our hosted firewall or VPN server.

Thanks.