Problem	Solution
Units was turned off and you need to re set it.	Turn the 'On' button to 'On' position, and press the two(2) buttons at the same time to set back to zero.

DISCLAIMER: Please note that the information contained herein is generalized in nature & can not account for all possibilities. Any proposed remedies for specific situations should not be considered as absolute or all-encompassing. Please seek professional assistance if there is any doubt as to the efficacy of a remedy or of the exact nature of any encountered problem. American Dental Accessories provides no warranty expressed or implied for any purpose and provides the information contained herein only as a service to those interested parties.