Could be a combination of things. So you'll need to start a process of elimination.
1) Try a known working charger in your tablet or try your charger in another device.
2) Do the same with the charging cable. So you end up with a known working charger/cable combination.
3) Carry out a diagnostic on the battery via the support tab in the members app.
4) Have the device inspected by an authorised Samsung centre.