The CO2Buddy has a large issue that relates to condensation build up within the unit. This issue can be a cause of any dampness, humidity or temperature changes that the unit has endured. unfortunately these changes don't have to be rapid for a condensation issue to occur, they may only be small changes in temperature that will cause a condensation issue.
The main way to solve this issue is to leave the unit in a dry and warm place for a few hours or even over night and then fully charge the unit until it is in normal operation.
Sometimes units may also need to be calibrated after being left to dry out, you can do this by following the diagram below.
(this is from the quick start guide under section 7)
If this still hasn't solved your issue please contact support at firstname.lastname@example.org