Ive had the same issues with Terrova. Changed battery the first time and it worked. Happened again and changed the battery with no luck. Tried to see it the unit had to re-learn itself and that didn’t work either. Finally took a knife and bent negative battery terminal up and positive terminals in so they make HARD contact. Seems to work for now. Maybe when I changed the battery the first time it had just made decent contact. Then after being used and bounced around it just lost some contact. Fingers are crossed.