405 error on hitting a URL that calls a Python flask api

The URL https://cliosuite-292503.ue.r.appspot.com/appointment?email=jaryya@gmail.com&email1=cliosight@gmail.com&contactName=Jigisha_Aryya&yourName=Jigisha_Aryya&start=11/05/2020_12:29_AM&end=11/05/2020_1:29_AM&callTitle=Titlesssss&callDesc=skdskcjhdsbchsb&file1=&file2=

is used to send an email invite for a 1-1 Video conference. But I am getting 405 error when the button is clicked to send the emails in the HTML. The application is collab.cliosight.com Please try and check the browser logs. It is a part of my project Cliosuite - suite.cliosight.com

The js function has:

$.post("https://cliosuite-292503.ue.r.appspot.com/appointment?email="+contactEmail+"&email1="+yourEmail+"&contactName="+contactName+
                                "&yourName="+yourName+"&start="+start_cs+"&end="+end_cs+"&callTitle="+
                                callTitle+"&callDesc="+callDesc+"&file1="+file1+"&file2="+file2, function(data, status){
                if(status.indexOf('200')>0){
                        alert('Meeting details are sent. Please check your email after some time.');}
 else {
                    alert("There was some issue in sending the conference details. " +
                                "Please try again later or contact support@cliosight.com");
                }
            });
        }