rgomez on "[Plugin: MailPoet Newsletters] Post selection hangs on "Loading results..." console shows a 500 Internal Error"

Hello.

I'm using PHP 7.0.2, MailPoet 2.6.19, WordPress 4.4.1 on a Windows 2012 R2 Server, all patched up.

I just noticed that I can't insert posts/pages into my newsletter: the window stays without any result, and the Loading Results... just keeps spinning.

Looking at the console in Chrome I see this:

POST http://<edited>/wp-admin/admin-ajax.php 500 (Internal Server Error)send @ load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,underscore,quicktags&ver=4.4.1:5m.extend.ajax @ load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,underscore,quicktags&ver=4.4.1:5s @ admin-campaigns-articles.js?ver=2.6.19:1(anonymous function) @ admin-campaigns-articles.js?ver=2.6.19:1j @ load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,underscore,quicktags&ver=4.4.1:2k.fireWith @ load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,underscore,quicktags&ver=4.4.1:2m.extend.ready @ load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,underscore,quicktags&ver=4.4.1:2J @ load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,underscore,quicktags&ver=4.4.1:2

Enabling Debug on wp-config gives me the following:

[15-Jan-2016 18:34:34 UTC] PHP Fatal error:  Uncaught Error: Function name must be a string in D:\inetpub\vhosts\<edited>\httpdocs\wp-content\plugins\wysija-newsletters\core\base.php:395
Stack trace:
#0 D:\inetpub\vhosts\<edited>\httpdocs\wp-includes\plugin.php(525): WYSIJA_help->ajax('')
#1 D:\inetpub\vhosts\<edited>\httpdocs\wp-admin\admin-ajax.php(89): do_action('wp_ajax_wysija_...')
#2 {main}
  thrown in D:\inetpub\vhosts\<edited>\httpdocs\wp-content\plugins\wysija-newsletters\core\base.php on line 395

Any idea of how to solve this?

Thanks.

https://wordpress.org/plugins/wysija-newsletters/