I had the same charging problem as everyone else. Tablet works great for a while, but suddenly it wont charge or it charges very slowly. I bought a new adapter, I tried all the fixes I found online, I did everything, still the slow or absent charging.
Then Eureka! I discovered a cheap, easy fix that continues to work for me a year later:
Buy a new USB cable.
Even if your present one looks undamaged and charges your phone just fine. Your tablet needs a new one. The new cable will work for a month or so, then you'll run into charging problems again. No worries, just buy a new cable again and you're good to go. Until next month.
As to why this laughably simple fix works, I read somewhere that the tsblet takes a lot of juice to charge, and the adapter just barely supplies enough. If the cable sustains any kind of wear and tear, the power dips just below what's required and proper charging cant happen. I have no idea whether this is actually the reason, but I have had no further problems with charging now that I regularly replace the cable, and it's been over a year now.