If ERR9 shows on your screen, it is an indication that weak batteries have been in the unit for too long.
First, try to replace your batteries with brand new alkaline or Lithium batteries. They must be non-heavy duty batteries.
Read more on What batteries can I use with my breathalyser?
If this issue still persists after replacing all batteries with brand new ones, you can contact us by clicking on "New Support Ticket" above