Make sure you have spelt the toon names correctly and that all toons have every toon in your team in their team list. Choose one to be the master and set that to be the master on both toons.

In the Core: Communications section, make sure both toons have exactly the same channel name and password. Then log out on both toons and log in again. Wait 15 seconds and they should see each other.

If this doesn't work, trying clearing the chat cache on both toons.