I had the same issue on one of my Finder 167's. I believe it's a problem with the board. If you hook up the mod to Escribe and then set the battery type to Power Supply and then Upload Settings to Device it will probably work. You can't operate the mod that way because you will have no battery protection (it won't cut off when the batteries are low/discharged because it's meant to be used when you are using a power supply). It is just a test to tell you whether the mod still functions. If it works in Power Supply, then it's probably an issue with the battery balancer/monitoring circuit. At least it will give you an idea what the potential problem may be. Good Luck!
PS When you hook up the mod to Escribe and click on the mod tab, make sure 2 cells are still selected and not 3 (I figure it's still 2, but it won't hurt to check). I'm pretty sure it's the battery balancer/monitoring circuit, but it won't hurt to check.
If the mod is less than a month old, I would try to get it replaced.
Cheers,
Steve