Javascript formats email in Outlook 2013 and 2016 but not in Outlook 365

I am in need of some help, I also want to make it known I am still fairly new to this type of coding and I code everything in notepad. I currently have HTML files that sit on a shared drive with Javascript files. These are not connected to a server. So I think Php use is out or I haven’t grasped the concept of how to implement it, But what I was able to create was a “HTML form” that my representatives can input data into and depending on the selections it will create a number of different things. One of which is an email, and the email will create properly in Outlook 2013 and 2016.

Office 365 is slowly rolling out and I am finding that the email doesn’t create properly. The To, subject and body all end up in the “To” Field. I have tried googling and looking on SO to see if there was anything reported but can not find anything. Any help or pointers on where to look would be greatly appreciated.

Sorry if the code is not up to standard, it is what I made from reading and trial and error. Code critique is welcome as well

function sendMail() 
{   
    
        // variables for form selections
        let ma = document.getElementById("MA").value;
        let hub = document.getElementById("Hub").value;
        let nod = document.getElementById("Node").value;
        let twn = document.getElementById("town").value;
        let phn = document.getElementById("phn").value;
        let nme = document.getElementById("nme").value;
        let loc = document.getElementById("loc").value;
        let rfr = document.getElementById("rfr").value;
        
        let imp;
        let prsn;
        
        let mafull;
        let cphn;
        let cnme;
        
        //Variables for mail
        let m_to;
        let m_subj;
        let m_body;
    
    //looks to see if contact name and phone are blank, assigns string to add into email body
        if (phn != "") {
            cphn = "Contact phone number is " + phn
        } else {cphn = ""}
        
        if (nme != "") {
            cnme = "Contact name is " + nme
        } else {cnme = ""}
    
    if(checkRadio.value == "Impacting") {
            
        imp = ' - Customer Impacting';
    }else {
        imp = ' - Not Customer Impacting';
    }
    
    // Replace abreviations with Full Ma Name
    mafull = ma.replace("CNY","Central New York").replace("ALB","Eastern New York").replace("NNE","Northern New England").replace("SNE","Southern New England").replace("WNY","Western New York").replace("HV","Eastern New York")
    
    m_subj = "Refer to Construction - " + mafull + "/" + hub + "/" + nod + "/" + twn + imp

    m_body =  "Reason for Referral: " + rfr + "%0D%0A" + "Refer to Construction - " + checkRadio.value + " reported at " + loc + "%0D%0A" + cnme + "%0D%0A" + cphn
    
    document.location.href = "mailto: " + ConstContact + "&[email protected] &subject=" + m_subj  + "&body=" + m_body
    + "%0D%0A"


}