Know nothing about the Hudl, but I have an android tablet which according to the blurb had no 3G connectivity. One day I plugged in a Huawei dongle, just as you did, and after a few minutes it connected. I think android has built in connectivity for a limited range of dongles. How long did you give it to connect? Perhaps a bit more investigation about suitable dongles is required. Someone else on the forum should be able to help.
Xiaomi Mi Mix 2 review