How to fix ‘Share option’ error in FB Instant Game

Question

This sharing code isn't working for desktop share but working fine in mobile share. In desktop i'm getting error.

function getBase64Image(img) {

    var canvas = document.createElement("canvas");
    canvas.width = 614;
    canvas.height = 1079;
    var ctx = canvas.getContext("2d");
    ctx.drawImage(img, 0, 0);

    var dataURL = canvas.toDataURL("image/png");
    return dataURL.replace(/^data:image\/(png|jpg);base64,/, "");
}


function fbShare() {


FBInstant.shareAsync(
    {
        intent: 'SHARE',
        image: getBase64Image(document.getElementById('loveimage1')),
        text: 'What type of lover are you? Find Out. Share. Win.',
        data: {
                myReplayData: '...'
            }
    }).then( function()
    {
    console.log("sharing is done");
    })
    .catch( function(err)
    {
    console.log('failed to share: ' + err.code + " :: " + err.message);
    });
};