If you can't see the chat button after being deployed and you have the component Admin Tools installed on your Joomla site, this can be affected by the Admin Tools Component settings.
During the loading of the Activehelper Live Chat button you can see the follow error using the Firebug : ReferenceError: startLivehelp is not defined
Obvious the configuration of the Admin Tools is different from one site to another but this is something very common that can help to find quickly the problem.
Step 1 : First and most important part is to "add" the ActiveHelper Live Chat Core, the follow is the path to the CORE folder ": \components\com_activehelper_livehelp\server" and "Allow direct access".
Step 2: Also you need to turn off "Protect against common file injection attacks", this option block the chat pop-up because the URL contains several variables.