There's no need to visit
http://chat.cohtitan.com -- nothing about Paragon Chat currently makes any use of that website.
To check your account, visit
http://cohtitan.com and log in. Then scroll to the bottom of the account management page to look at the "Titan Projects" section. If it says "Paragon Chat: Your account is ready for Paragon Chat!" then are you set. If it says "Paragon Chat: Your account cannot currently access Titan's Paragon Chat server because your username does not meet our username requirements." then you'll need to change your username.
Logging in on the Titan main site also ensures that you have the proper password. Logging in on the forums does NOT assure that! We apparently didn't lock down the ability to change your password via the forums until just this past week. if you ever changed your password or email through the forums, then your forum account is out of sync with the rest of your Titan account. You should log in to the Titan main site to verify that you can log in properly, and if necessary update your email and password. If you can't log in to the Titan main site, you won't be able to log into Paragon Chat either.
Before Paragon Chat launch, you may
optionally log in to the chat server using any XMPP client. This isn't required and if you have no idea what an XMPP client is, feel free to just ignore this paragraph entirely.
Once Paragon Chat launches, you'll be logging in to it through a desktop application that will be distributed. It still won't involve visiting
http://chat.cohtitan.com though.