From what I have seen, there are more ports that need to be opened. I have the same issue and I am still researching. If I find anything out I will post an update.
Edit--- Wow, didn't see this post was from last May, and there was no reply from support?
You might want to open an actual case with them, its hit and miss about them responding on the forums. I know that with K2 there are other ports that are active, but if your client has an aggressive firewall config, that may be the case.