Unacceptable - SENSORS not working!!

So at the end of last year I moved to Discovery Insure, and was made aware that i needed to get a tracker/sensor installed in my vehicles (2). In January and February this year it worked fairly well until I had a 3rd vehicle added. Since March, although at a reduced utilization, it has been verified that the trackers/sensors (all 3) are either not recording the trips or only part of the trips. Not acceptable as one doesn't mind paying a slighter higher premium, if he does get the rebate as promised according to the driving history/behavior.