Have you tried a new coil on it to see if it works properly again? Being an all in one unit nothing is serviceable if it went out, could just be the internals gave out. If it's under warranty consider getting it replaced. I used to use halo's triton pens but gave up on them and went to a regulated mod with rta's and rda's.
Maybe I just had bad luck with them but I noticed a decline in quality. The original kit and the first several replacement items like polycarb tanks, driptip top caps etc lasted awhile. The coils lasted a good 7-10 days. After a few months I noticed the top caps were breaking more frequently. They'd just crack or the threaded insert would pull out like the glue used let loose. The tanks began cracking and leaking (more so with the newer ones). The batteries started dying and would have issues firing (only a single push button so as simple a device as possible). The coil/wick combos started dying within a matter of 1-3 days. The juice I was using hadn't changed.
My mom had the same issues with hers, the coils were burning out fast. She'd fill the tank, soak the wick, vape the tank down then refill - boom, dead coil. When her batteries died she got the larger 900mah pen battery. Contacted halo and after several emails back and forth with non helpful customer support, they asked what device she was using. After telling them the newest battery was the 900mah, they blamed the dead coils only lasting a day on their own halo branded pen battery. They said basically that the higher mah allowed the battery to run closer to it's max 4.2v for longer (which makes sense) and that's why. She even tried different resistance coils. Same issue.
Long story short, their customer service sucks, they don't seem to have a clue about their own products, don't stand behind their rather high priced items and when things like coils die much sooner than they should they just talk gibberish and blame the customer. They have a couple of ejuice flavors I like but beyond that I won't bother with them anymore. Most of their advanced regulated devices are eleaf products they've slapped their logo on and can be found cheaper elsewhere.
If they won't replace it or give you a hard time but you like the device, consider looking for the joyetech ego mega twist. It's the same size, button layout, mah capacity etc. and I'd be willing to bet it's what halo's put their tracer logo on. MyVaporStore has them for $21.95 + shipping. Other places may have them for less, I didn't search very hard.
https://www.myvaporstore.com/Joyetech-eGo-Mega-Twist-Plus-Battery-p/joye-mtb.htm