SSL cert breaking

I got around this exact same issue by taking the ajax-loader.gif from the CF& plugin folder uploading it into media directory then adding a custom function via this plugin https://www.ads-software.com/plugins/functionality/ (or indeed you could add it directly into to your functions.php or child functions.php) depending on your template setup. Change the URL path to your own and et voilà!

/* Custom ajax loader for CF7 so SSL cert doesn't break */
add_filter('wpcf7_ajax_loader', 'my_wpcf7_ajax_loader');
function my_wpcf7_ajax_loader () {
	return ('https://www.YOURSITE.com/wp-content/uploads/YEAR/MONTH/ajax-loader.gif')';
}