I purchased this unit for a dog I had that was having knee issues. I wasn't able to use it because surgery was his only option, he had a torn acl. So I stored the unit in the box. I now have a new dog who is having some issues so thought I would give it a try. I pulled out the unit, it would not turn on. No problem, I pulled out the charger and charged it. The unit blinked on and turned right back off. I contacted Miridia and they suggested a new charger so I did that. I got the new charger, charged for over 2 hours, same with the unit it blocks and turns back off. The company's response was sorry it may be out of the units lifespan. So basically, it cost a fortune and has a short life span.