MacBook Pro unable to connect to iPhone Personal Hotspot

For the last couple weeks, I've been unable to connect my MacBook Pro to my iPhone using the phone's personal hotspot. If I turn on the hotspot, the phone appears on the computer's list of available wifi networks, but if I try to connect the computer, an error message appears that says the computer is unable to connect to the network. I also tried connecting them with blutooth, but I could not get the computer and the phone to "pair."

I've been using my hotspot periodically with my laptop when I travel, as recently as about a month ago, so this is a new problem. I was able yesterday to connect my computer to another iPhone's personal hotspot, so I think the problem is with my phone and not my computer.

Specs:

The computer is a MacBook Pro purchased in early 2012 (so it's a late 2011 model). It's running Yosemite OS X 10.10.4

The phone is an iPhone 5 with iOS 8.2.

My wireless service provider is AT&T, and I have a "mobile share plan" that allows the use of the personal hotspot.

Any suggestions for how to address this problem? Thanks.