Whats going on redirect with the Ipad.

I am accessing the FABO site using my I phone without issues, when I use a local WIFI.
If I turn WIFI off and use my phone plan’s internet service I get the pop-up.
I don’t recall ever seeing the pop-up when I use my PC based desk top or lap top. But of course the PC based computers have up to date anti virus programs on them.
The I phone does not.