admin-ajax.php mixed content

You shouldn’t do something like this in your JS code:

url: 'https://'+window.location.host+'/admin/admin-ajax.php',

You should use wp_localize_script and pass proper URL in there.

Let’s say your AJAX call is located in file my-js-file.js. Somewhere in your theme/plugin you have something like this

wp_enqueue_script( '<SOME_HANDLE>', ... . 'my-js-file.js' , ...);

You should add this after it:

wp_localize_script( '<SOME_HANDLE>', 'MyScriptData', array( 'ajax_url' => admin_url( 'admin-ajax.php' ) ) );

And in your JS file it should be

$.ajax({
    url: MyScriptData.ajax_url,
    type:'post',