Dare I suggest it & I wouldn't normally, but whilst you're changing ports, disable your software firewall temporarily. Try again.

Don't forget to contact the company involved. They will know something about how to solve the issue ... if their or if not the ones who are responsible. Ask them about the equipment or whomever you obtained it from. And ask them "How to open ports" on your equipment or that the isp might be blocking. Insist to them that you're aware port 6346 is blocked.