How to debug fortitoken push notification

Hello,

I have configured Fortitokens with push notification on my Fortigate 601E a few months ago and everything was working ok and the users were receiving the push notifications on their mobile devices were they have Fortitoken mobile configured.

Last week without any notice or configuration change some users (myself included) stop receiving the push notifications, and can only loggin after inserting the token value.

How can I debug what is the problem for this users not being able to receive push notification on the Fortitoken mobile.

Best regards.

Eduardo