Not receive new plugin update notifications.

Hello,

I have two WordPress sites and hosted on an Ubuntu 12.04, Nginx VPS. This plugin doesn’t give me plugin update notifications (both sites). But it gives new logging notifications. I guess this is not a WordPress cron issue, because other scheduled tasks run smoothly specially backup plugins.

What could be the issue?

CKPN Version:             1.9.3.1
WordPress Version:        4.1.1

PUSHOVER NOTIFICATIONS SETTINGS:
application_key: [removed for display]
api_key: [removed for display]
new_user: true
new_post: true
post_notification_role: administrator
new_comment: true
notify_authors: true
password_reset: true
plugin_updates: true
core_update: true
sslverify: false
multiple_keys: false
logging: true
new_post_roles: Array

https://wordpress.org/plugins/pushover-notifications/