Remote Assist API

Hi,
I am trying out ZOHO API for ZOHO Meeting. There is "createRemoteAssistance" api which i am interested. However, when i tried to test the URL ie: POST method, the returned xml say "Specified apikey [my key] is not valid.Provide a correct one."

I had checked and tally that it is the correct API key gen for my ZOHO account(zapi).

Though i am a Free Partner user for now, as i need to confirm this is working solution before i can upgrade to be Commercial partner.

Any help is very much appreciated. Thanks in advance.