My pole light stopped working. I replaced the bulb (35w High Pressure Sodium), but it didn't help. The only thing on the pole itself is the little round light sensor. I don't find a switch in my fuse box that is labeled for this. Any suggestions?

Each HPS fixture has a small transformer called a ballast inside. Assuming there is voltage to the fixture and the photocell is working, the ballast is the problem.

Often times it is cheaper to buy a new fixture rather than a replacement ballast. You can do the shopping and compare prices.

Did you try to replace the photocell? If not that is an easy, cheap, try.
These do go bad. They even sell them in home centers.

Do I not need to turn off the power to do either one of these? I'm not sure how to do that when there isn't an on/off switch or breaker switch for it. Thank you for any further direction.