penDirector does not recognize that the pen is incorrect for chosen firmware
We have found that it is possible to upgrade an IO2 pen with the DP-201 firmware. penDirector does not recognize that the pen is incorrect for that firmware and this will cause pens to fail.
This limitation (i.e. check if the pen was IO2) was removed in most recent versions of penDirector (from 2.6 onwards). So if you are still upgrading the firmware of your IO2 pen, be very careful not to use wrong firmware.
The check has been replaced in penDirector version 2.8.0.