Over the last few days I have been getting a message in the middle of the screen which says, 'Cannot establish a secure connection'
There is no option to fix or to look at the details. All you can do is touch the 'ok' button. Then it goes off. Five minutes later, it appears again again.
You could try checking to see what Apps are actively running and close each in turn to check if the message stops appearing. Hopefully that way you may be able to at least identify the 'culprit' App.
Try (quote):-
'Hold the "Home" button on the tablet until the "Task Manager" app appears on the screen. All active apps are listed in the Active Applications section. Tap the "End all" button to close all apps running on your tablet. You can close individual apps by tapping their "X" icon in the Task Manager.'
I get that quite often on my Galaxy tab. It only happens when I am using a router other an my own (hotel wifi) I don`t worry about it and just keep clicking 'OK'
To find / isolate the App that is displaying the message, when the message appears on screen, suggest that you then stop an App to see if the message stops displaying.
Just a thought, if your date and time are incorrect on your Galaxy it is possible that would trigger the sort of error message you are seeing. To eliminate that possibility, make sure the date and time are set correctly.