If you are on an mvno that does not allow Internet Sharing it does not work with the native WP setting/App as it does not attempt to mask the sharing and your carrier declines the connection.
That is a issue with Cricket for sure, although I did get the 920 to work there through the use of the foreign sim trick.
Trying to get the 1320 to work on Straight Talk, in the past, prior to the 1320, I was able to use internet sharing there, even using the foreign sim doesn't work, any suggestions.
I'll be using the BLU phone tonight on Straight Talk, hoping for the best as I use internet sharing extensively at work, often out in the field on construction sites.