Please be aware that you neeed to update the security certificate for iOS push notifications on your IBM Sametime proxy servers before July 18th. Otherwise push notifications to your iOS devices will stop working. Instructions how to download and install
Sametime 8.5.1: No user/password prompt in iPhone web client
If you are using the Sametime 8.5.1 web client for the iPhone and only the Sametime logo is visible and there is no prompt for user and password to login, then you might have disabled guest logins for web clients.