Tablet can't find iPhone hotspot?

I recently got the Microsoft Surface RT and am trying use the Internet by connecting to a hotspot I set up on my iPhone 4S. My hotspot is turned on from my phone but doesn't show up on my tablets network connection lists although it works when my sister does it with her phone, what can I do to fix this?

Please state your sister's system. I know Android, a self-help HotSpot via rooting and a Google-built Android HotSpot has a difference that lends itself to exactly the problem you have, but of course distance and signal strength might also enter the mix by mistake.

Same to a little test I did to Nokia/Symbian; idea is this: apps ran in user-space; but Google-built as part of Gingerbread was in full permission to kernel. So apping HotSpot can only go as far as Peer mode; while Googling can go further to true AP mode for fellow Android devices to Wi-Fing to.

Best way to test out: have a PC a USB Wi-Fi, turn on HotSpot in iPhone; Windows can use both mode so let it to tell you which mode the HotSpot is in. You don't want it to be Peer/Adhoc but that's not in your control, perhaps it means ditching and being a turncoat to iProducts?