Issue on passing parameter to a prompt

[xumes]

I created a sample report, with only one prompt: pMes but, when calling it, the body on response is:

<rds:error xmlns:rds="http://developer.cognos.com/schemas/rds/types/2"><rds:message>RDS-ERR-1021 The IBM Cognos report "storeID("i7C45039AB6C148C597E12CD3D2080FC8")" could not be run because it contains unanswered prompts. Please provide the prompt answers, and run the report again.</rds:message><rds:promptID>iFD2495DC224C456BB33BBBC1EC159BBF</rds:promptID><rds:url>http://zcogwass1.boulder.ibm.com:9305/bi/v1/disp?b_action=xts.run&amp;m=ccs/ccs_prompt.xts&amp;promptID=iFD2495DC224C456BB33BBBC1EC159BBF&amp;ui.object=storeID%28%22i7C45039AB6C148C597E12CD3D2080FC8%22%29&amp;ui.routingServerGroup=core</rds:url></rds:error>

my QueryString is:

        let qs = {
            pMes: 'Jan',
            fmt: 'HTMLFragment'
        };

any help is appreciated.