Zoho PostMessage API returns 1108 Domain not registered

Question

I'm using postMessage API to post a save command to my Zoho writer iframe. Following the docs I have this

        XDC.setTarget({
            "origin": "https://api.office-integrator.com",
            "window": document.getElementById("zoho-writer").contentWindow
        });
        XDC.postMessage({
            "message": "SaveDocument",
            "data": {
                "hideSaveButton": true, // Default value will be true
                "forceSave": true, // Default value will be true
                "saveUrlParams": JSON.stringify({ apikey: "<my key>" }),
                "format": "docx"
            },
            // Use "SaveDocumentResponse" event for oncomplete
            "onexception": function(data) {
                var x = 1;
            },
            "oncomplete": function (data) {
                var x = 1;
            }
        } );

I'm just guessing on the saveUrlParams because they don't explain that other then to say it is some JSON. Whenever I run this I get the onexception response with code 1108 and a message of Domain not registered. I have gone in to my Zoho account - the White Labeling - Security Controls - PostMessage domain and added my domain.

Any thoughts?