Had the same problem with my Samsung Tab 2. Hadn't used it for quite a while and decided to try it. Ordered a new Samsung cable for £1.50. Cable came, plugged it in and it wouldn't charge. Tried everything advised above and still no joy. I had the cable plugged into the Samsung fast charger, looked for the original charger, found it, plugged it in and it started working straight away. I now have a fully charged tablet. So yeah make sure you're using the correct charger as they seem to not like other chargers.