IIRC when you go to ISE the browser needs to have cookies enabled, as that is how ISE maintains the session information. Check to see if you are allowing cookies in those devices.
Alternately could also try loading the page on the WLC directly and testing it there.
Sent from Cisco Technical Support iPhone App
Yes, the wierd thing is that it is not a consistent error/problem.
If I take the iPad as an example.
With some tests it works, other times it gets a network error before the redirect page and some times it get it after authentication.
With Android it's more or less before the redirect page, you see the https://ise01.x.coom/xxxx...cwa in the browser but you get a 'Web page not available'