What network are you using it on? CDMA networks like Verizon only use the SIM for LTE, so that would raise the possibility that it just doesn't like your SIM at all. But "H" implies HSDPA, which is a GSM 3g technology and so would need a SIM. And if you are using a different network there's always the possibility that it's not fully compatible. So if you can tell us who you are trying to use it with, and what else does or doesn't work, that might narrow the problem down a bit.