You have received the following alert:
iOS Distribution Certificate Expires in 30 Days
The iOS Distribution Certificate comes into play during the upload process. It's not the same as a push notification certificate, so you don't need to worry about it or if it will have any effect on the push notifications failing when it expires.
The Distribution Certificates are automatically renewed when the Apps are loaded to the Customer's Developer Account, so it is taken care of the next time you publish an App.