I had trouble in the past where cleaning the contacts with alcohol (both device and charger) fixed the charging issue.
Probably 6 months ago (maybe longer) my band wouldn't charge even after cleaning. I tried putting in fridge, tapping it, different chargers but it refused to charge. I put it up for a couple months thinking it was done for. I came back across it one day & plugged it in to show my bf how it wouldn't light up or anything BUT to my surprise it actually started charging. I was so happy because I'd been lost without it but I noticed the battery level would get to around 40% then the next thing I knew the band wouldn't be syncing data and when id plug it in it'd only have one light, like it died right after getting to like 40%. I could live with that but a couple mts ago it finally stopped for good I think. I'm pretty sure the battery is just done for at this point.