Trouble with wifi

I have a windows venue 8 pro that was working fine. Now all of a sudden it won't let me login. It says "Your PC is offline. Please sign in with the last password used on this PC." None of my passwords will work. The wifi button shows a red x through it. When I click that button it comes up with switches to turn airplane mode on/off (it is off) and wifi on/off (it is off). I slide the button to turn wifi on but it slides backoff. All other devices can connect to wifi, so it isn't a problem with our wifi. How can I get my tablet online?? How can I log in?