XSS 406 Not Acceptable trying to get multiple page information

Question

My school currently has a website that it puts our courses on. I have been trying to improve some of the information that it displays on the main page by requesting other information on other pages and place them on a side bar via a chrome extension. I have to login when trying to see this information and it is HTTPS. However I can pull grades from another page. But when I try to pull assignments, it ends up sending back a GET 406 Not Acceptable Error.

function removeElements(){
    $("aside#right-side").children('div').remove();
    $("aside#right-side").children('h2').remove();
    $("aside#right-side").children('ul').remove();
}

function addDivs(){
    $("aside#right-side").prepend('<div class="events_list"><h2>Upcoming Assignments</h2><div class="assignment-summary-div"></div></div>');
    $("aside#right-side").prepend('<div class="events_list"><h2>Grade Summary</h2><div class="grade-summary-div"></div></div>');
}
function getInfo(){
    $(".grade-summary-div").load("grades .course_details");
    $(".assignment-summary-div").load("assignments .assignment_list");
}

Now from my understanding I don't need to authenticate or use the api if I am already logged in. I might be wrong, but that is why I am here. Why am I getting the 406 error?