We suggest that you check that  the battery has sufficient  charge, if the battery is running low the Mitt Hotspot may continue to massage but will not heat.

[PAUSE 10 SECONDS]

There is a safety cut off to turn the hotspot heat off if it gets too hot (this may happen through repetitive use/use on v hot days/being stored somewhere too warm). Unfortunately, it doesn’t have the technology to turn back on if it starts to cool, but if you are trying to turn the heat on and it is repeatedly turning straight back off again - so long as previously it worked fine/the battery is charged, then this could be the cause.