Try a few things:
1. Try forgot network.
2. GO near the modem, see if it works.
3. Try at a hotspot near you, or at a friend's. If it does, your router is t fault.
4. If none of the above works, try a hard reset of your tablet.
5. If none f the above works, your antenna is faulty.
Guys, before posting here, please do a google search. A lot of these issues are addressed previously elsewhere.