I was able to get it working on dot-walked fields, but I had to create a copy of Macro, use a different function name, and I used an if/else statement in the macro so it would work on the requested for field no matter which form I was on.  We have a custom u_requested_for field, so your script may be a little different, but here's what I used:

 

function openLink2(ref) {
var tck = g_form.getValue('number');
if(tck.indexOf('TASK') >= 0){
var email = g_form.getReference('request_item.u_requested_for').email;
} else {
var email = g_form.getReference(ref.split('.')[1]).email;
}
var url = 'msteams:/l/chat/0/0?users=';
url += email;
url += '$[AMP]topicname=Chat';
window.open(url, "_blank");
}