Pls try these steps:
[] Ensure that there are no other file sharing apps running in the background i.e. ShareIt etc (they can interfere with the attempt to connect to a local wifi) - - next
[] Get access to the router and press the WPS button (manual authentication button) something like this
[image|1234503]
then tap the same icon you'll find in your tablet (wifi advanced setting ).
[] if it works, great! if not, your neighbor maybe blocking your tablet from connecting. He (I mean he or she) checks his router settings and ensure tablets arent blocked or your tablet's mac ID isnt blocked. I assume he knows how to do it.