Send to messenger button not showing on mobile devices or incognito windows

I have a Send to Messenger button that is working just fine on desktop computers (all browsers) but on mobile and tablets (at least iOS ones that I tried) it is not showing. I tried to see the console, it doesn't throw any message at all. It just doesn't display it.
The code I am using is:

messenger_app_id="app_id"
page_id="page_id"
data-ref="data_ref"
color="blue"
size="large"
cta_text="SUBSCRIBE_TO_UPDATES">
</div>

<script>
window.fbAsyncInit = function() {
FB.init({
appId : 'app_id',
autoLogAppEvents : true,
xfbml : true,
version : 'v12.0'
});
FB.AppEvents.logPageView();
FB.Event.subscribe('send_to_messenger', function(e) {});
};
</script>
<script async defer crossorigin="anonymous" src="https://connect.facebook.net/el_GR/sdk.js"></script>

I want to have this fixed and make the send to messenger button show on every environment/browser and if the user is not logged in or has a session stored, so show the login to facebook button (that should be done automatically by the send to messenger plugin I guess)