Referencing the example in the
documentation, be sure that clarity login has all XOG/rights. Also the username and password in Custom Script Parameters Tab should match with the one in GEL Script.
<gel:parameter default="http://nikuvm:80" var="XOGURL"/>
<gel:parameter default="svong" var="XOGUsername"/>
<gel:parameter default="svong" secure="true" var="XOGPassword"/>