Third ride with my Powertap G3 this past weekend, and things didn't work correctly from the beginning (no issues at all on previous 2 rides). The power numbers being displayed on my Garmin Edge 500 seemed to be missing the 2nd and 3rd digits. I was hoping that the last two digits were being recorded to the data file, but that was not the case either. At the 1:33 mark, the power numbers came back and stayed until 1:48 into the ride. The cadence functionality worked from 0:00 until it dropped out completely at 1:48. Total ride length was a bit over 2 hours. Anybody have an idea what might be happening?

0:00 - Power numbers seem to be first-digit only; cadence works
1:33 - Power numbers start working
1:48 - Power numbers seem to be first-digit only again; cadence stops working

Mine did that, battery change fixed it. Particularly likely if it is new and you are using the battery that came supplied with it

Also while changing the battery, hook up to the computer and check for firmware updates, early versions drained the battery in about 3 weeks. Latest version gets months out of a battery