The pty parameter is in both configs, could you try changing one of the client configs tweaking that? Then try, it's just a hunch, but something in me says to try it. I realize it's a sms name but it doesn't have to be that.

I cant change the pty value of the client configs as that defines the vpn server.

I have done a line-by-line comparison of the output of the pon commnd with the debug flags from both clients and the pptp options are identical. One client connects and the other does not so the issue lies elsewhere.

My first guess is that the error is related to both clients being behind the same nat firewall and the first tunnel is somehow preventing the second tunnel.

I can connect from my macbook from a different location so the server is able to serve multiple tunnels. I think it must be the client nat that is tripping this up.