Hey Giovanni,
May I know whether you have set up Amazon S3 storage previously? Because the error occurs when the cron is trying to pull the files from amazon back to your site but your Amazon settings were already removed, causing failure(
http://take.ms/MOjGI).
As you can see in your files table(
http://take.ms/YG7Vf), there are still files stored in Amazon S3. If you want to stop using Amazon S3 as storage, you have to get those files back to your site.
For now, perhaps you can set up Amazon S3 again to pull back those files into your site, then remove Amazon's settings again, if you do not want to use it.
EDIT: I have helped you temporary comment out
this code in the file
JoomlaFolder/administrator/components/com_easysocial/includes/cron/hooks/storage.php.
This will allow the cron to work for now. If you want to set up Amazon S3 to pull those file again, you need to un-comment out that line of code.