In an email to users the company said:

Today we made  a major update of the app and all our other systems. Until you install the new version your app will not work. Please go to the app store on your IOS device and update the app.

We now charge all new Chat Center users $1.99/month per Chat ID. As an existing user you will receive 12 months free, starting from today.

The new app has many new features. Most importantly it has a new address https://chat.center. The old https://chatcenter.me address will continue to work, but your chat name is now http://chat.center/yourchatname
We have especially optimized the app for business use. You can put your name on your web site, in email campaigns and indeed even your business card. See the app store for more details.

For the full update go to http://chat.center. There is now a full web version, including registration. Indeed, the app is only usable by those who register on the web site for an account.