The most common reason for an RBT IV to print a partial ticket or not print at all is low battery voltage.  The RBT IV has a 12 volt rechargeable battery located in the case foam.  The Alco-Sensor IV is powered independently by a 9 volt alkaline battery.  The print mechanism of the RBT IV demands more power than the other functions, and when the charge is low, the device may seem to be operating properly but will not print.  This is an indication that  your 12 volt battery needs to be recharged or replaced.  Plug in the battery charger and you should be able to print in a few minutes.  (View more information about charging your battery.)

Another scenario:
If the Alco-Sensor IV is not communicating with the RBT IV then you will not get a printed result.  Perhaps the cable connecting the two devices is damaged or the connector is not fully inserted into the port on the bottom of the Alco-Sensor IV. Check all connections and retry your test.

Lastly, if the operator does not follow the RBT IV instrument prompts in sequence you might insert the mouthpiece before the RBT IV is ready to initiate the communication process.  Always follow the display prompts exactly in the order they appear.