Long long time ago I had a device that would not accept a password with a & in the middle of it.  Just one random device - all others were ok.  So if you've got a decent password try one thats pretty simple (just letters say) and see what happens.

How old is the tablet ?

try,
change the hotspot ID/name
change the hotspot pass to 12345678 as a test (as above)

hotspots can sometimes be a pain in the a .