Have you tried moving the Tab around - closer and/or further away from the router?
Have you tried connecting to a public wifi - Library, starbucks, mcdonalds? Do those work?
Have you tried to manually add the wifi. At the bottom of the available-wifi, (scroll down), is "+ Add Wif-fi Network" and then followed the prompts? If it works, it is still better than not getting on even if a work around.