Typically, this is seen when a deployment is already activated with a different serial number. This error usually occurs when moving an existing deployment to a new PC.
The Epay software will give you the opportunity to deactivate/disassociate the current deployment ID associated with the current serial number.
You will be prompted to enter your deployment ID or search by demographics, if one is found, it will warn you that the found deployment ID is associated with an existing activated serial number.
Click OK and enter your deployment ID - this will deactivate the old machine/serial number and activate it on the new machine. You're now ready to process.