We've had resolved it in channel chat: Tixati User Group.
It boiled down to port forwarding, nobody had it. I've dug up old forum threads here and Tixati does have utp NAT hole punching support. If any single of his friends had ports forwarded then the connection would have worked, using that friend to start the transfer and connect to everyone (in theory).
If you are in a similar position: try IPv6. If your friends have it too, you probably can do port forwarding for IPv6 and only IPv6.
If IPv6 is not an option, please refer to the two VPN threads (don't get misled by the name):
VPN choice https://forum.tixati.com/support/6946
Tixati setup and troubleshooting https://forum.tixati.com/support/7011
The core requirement: the VPN provider must support port forwarding (e.g. VPN_IP:Port connects to your PC:Port, not some LAN router port-forwarding explanations that have nothing to do with the VPN)