Please do the following.
First upgrade the plugin to latest version (188.8.131.52)
Then enable the dev mode so we can find the issue later.
Then go to this url just once (this will unlock the queues) http://pucp.e-quipu.pe/wp-admin/admin.php?page=wordpress-social-invitations&support=yes and close the window (note that &support=yes is the one that will unlock your queue)
Give it some time to the queue to lock again and start processing all the items.
After some time check if the items in the queue went down, and if the queue still are locked.
All the connection and debug info will be written in your error_log file located in the root of your server.