I do not know what device you own, but AFAIK Garmin ships only USB cables with most of their devices, no chargers. So if you have a defectuous charger, have it replaced at the place where you bought it. If it is the cable that does not work, just buy a new one - it costs ~$1 on AliExpress (free shipping). It may be also just dirty or corroded contacts though, so make sure you cleaned them properly (both on the watch, as well as on the cable) before testing again.