This is probably a right issue.
I tested it out and it looks like it’s a bug. I did not have this chat button either with a standard user while the property is True…
I just checked the object responsible for adding the webjar for this Chat in the header.
(x+x+x+a to have access to advanced editors and edit objects on the configuration page, see the URL in the screenshot above)
Changing the Extension Scope from Current User (only one Administrator, the one that has edit right on the page) to Current Wiki was enough for my regular user to get the chat button.
@ppantiru might know more about this 
I opened Loading... to track the status of this issue.
Thanks for your report!
I hope this could help you a bit
Lucas C.