K6TU Remote via VPN problem

I am having problems connecting K6TU Remote client.  I have set up a Raspbery Pi Server running SoftEther VPN.  The radio is a Flex 6700.  On my Windows 10 PC I can set up a VPN connection to the remote site and the successfully run SmartSDR.  On my iPad I can set up a VPN connection to the remote server Pi and have proved that I can connect to the Internet via the remote site.  If I run a speedtest over the VPN I am getting 8mbps one way and 20mbps the other way so no issues there.  Now if I try and run K6TU Remote on my iPad, I can see the 6700 at the remote site, but I cannot connect to it.  I have tried the only settings I can find (High or Low Speed Data) but changing these makes no difference.  Any suggestions to get K6TU Remote to connect to the 6700?  Thanks Peter G3ZSS