I purchased this set a while back from woot and it never worked, emailed the company and was told they would not replace it, wanted me to pay shipping to return for repair. This product sucks!
Thanks, hffaulk63. You’d just saved me the $40 I was about to throw away. Did you try to contact Woot about replacement/refund?
Sorry for the problem. Looks like you bought it back in 2015 so it’s covered under IQ’s warranty. It’s not unusual for companies to ask you to pay shipping on warranty service. 
I bought one a couple months ago to replace my older TENS unit. It’s been working fine so far.