Bill,
If you suspect the SkyusDS is causing your trouble connect the modem directly to a PC withe the drivers installed and test your VPN connection.
The line of service in use with the SkyusDS, does it have a static unrestricted IP, or a Dynamic (non-routable)?
Feel free to call into Inseego Technical Support if you are having trouble with your SkyusDS We are available Monday through Friday 8AM until 5PM at 877-698-6481 or via technicalsupportus@inseego.com