Have you tried completely rebooting the tablet? I don't mean just turning off the display, but shutting it completely down for about 20-25 seconds and then restarting it. This is the simplest fix.
If that doesn't do it you might also try rebooting the router.
Lastly, if your home WiFi is password protected (aka locked) unlock it for your testing with the tablet. If the tablet will then connect, once it is connected, then you can turn back on the protection and see if it still works.
A lot of times it isn't the connecting device, but the router that is the problem.