chat plugin installed but not showing any users

Installed (www.wordpress.org/extend/plugins/buddypress-ajax-chat)buddypress ajax chat on my blog. (i am using latest wrdpress version+bddypress default theme).
i think installation was successful cause no errors was shown but it doesn’t showing any user online and text msg is not displaying after clicking submit button.
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what cud be the reason ?
–is this because of my 000webhost freeplan?
–or this thing requires more standard version of mysql or php thingy on my host?
–or do i have to edit mysql user,pass,database nam,host in the config file? it is currently ‘null’ (may b it means default)
—and i did chmod 777 thing but no result

>>answers will be gladly accepted.