phtml file getting downloaded

I installed a plugin for social login in WordPress / WooCommerce site.

http://goo.gl/63D174

When user clicks on any social network icon, it must be redirected to a page. However, the plugin or server is misbehaving and the file is getting downloaded instead.
I read several threads here and in other places that talk about adding AddHandler line to .htacess file. However it didn’t solve my problem.

I talked to my host support they told me the following::

The .phtml mapping appears not to be working because there are no .phtml files physically located on your account:

root@s1-india [/home/playseeb/public_html]# find . -type f -name \*.phtml
root@s1-india [/home/playseeb/public_html]#

ie. the file without any extension gets offered to be downloaded, with the contents

/*!
* HybridAuth
* http://hybridauth.sourceforge.net | http://github.com/hybridauth/hybridauth
* (c) 2009-2012, HybridAuth authors | http://hybridauth.sourceforge.net/licenses.html
*/

// ------------------------------------------------------------------------
//	HybridAuth End Point
// ------------------------------------------------------------------------

require_once( "Hybrid/Auth.php" );
require_once( "Hybrid/Endpoint.php" ); 

Hybrid_Endpoint::process();
-----------------------------------------------------

I am really not sure whether it is due to the plugins code, WP rewrites or the theme in which it is used as I have found no errors logged on the server, and no documentation for this plugin that would outline the issue.

Have you asked the developers whether the links such as

https://yoursite.com/wp-login.php?social_login=1&social_network=facebook&next=https://yoursite.com/my-account/

are correct, ie. if they should be like this?

I am sure the links are correct. Because it used to work until recently.