Error when calling QzhbCgiParse

This is posted to both the RPG and the Midrange-L mailings lists.

I'm using IWS to call a REST API. I'm using QzhbCgiParse to retrieve the
passed parameter(s) from the QUERY_STRING. When I call the API all I see
is a 1 page dump in QPSRVDMP in QEZDEBUG with the user data FFDC but
can't see anything other than
.SYMPTOM STRING-
5770 SP/QZHBCGI MSGMCH3601
I've used Google and the IBM API docs to research but I can't see the
issue. My prototype and same call follow.

Dcl-Pr QzhbCgiParse extproc('QzhbCgiParse');
cmdStr char(65535) const options(*trim: *varsize);
outFmt char(8) const;
targetBuf char(65535);
targetSize int(10) const;
responseLen int(10);
errorCode char(56);
End-Pr;

//--------------------------------------------------------------
// GetInputParameter Get the passed parameter from QUERY_STRING
//--------------------------------------------------------------
dcl-proc GetInputParameter;
dcl-pi *n varchar(100);
pSearchParameter varchar(20) const;
end-pi;

dcl-s cmdStr char(65535);
dcl-s outFmt char(8) inz('CGII0100');
dcl-s targetBuf char(65535);
dcl-s targetSize int(10);
dcl-s responseLen int(10) inz(0);
dcl-s errorCode char(56);
dcl-s pos uns(5);

cmdStr = '-value ' + pSearchParameter + x'00';
QzhbCgiParse(cmdStr:outFmt: targetBuf: %size(targetBuf) : responseLen
:errorcode);
dump(a);
If responseLen > 0;
pos = %SCAN(X'25':targetBuf);
Return %Trim(%Subst(targetBuf:1:pos-1));
Else;
Return ' ';
Endif;
end-proc;

I've commented out the call to QzhbCgiParse and the program completes
without error and produces a dump (dump(a)). When I uncomment the call to
QzhbCgiParse the program fails but produces no dump for dump(a). It does
however create the QPSRVDMP dump I mentioned earlier.

Any help would be greatly appreciated as I've come to a brick wall.

Thanks,

Rob