[More of a question/solution for others with the same issue]
So I recently switched from AT&T to Mint Mobile to save some $$$ -- Hell yea!
I live in the Bay Area (SF) and commute on the train. While on the train I tether to get some work done or whatever.
Normal tethering ceased to work to my Macbook Pro.
I googled, and read about all the APN configurations - added, selected others, rebooted after and tested, but to no avail.
I successfully resolved the issue using PdaNet
You'll need to install applications from:
Android App https://play.google.com/store/apps/details?id=com.pdanet
Simply follow the instructions and voila!
Good luck to others.