Try a soft reset, that is, press and hold the power button for 20 seconds. Release, then press and hold the power button for 2 seconds to power it back on. If it's not connecting at any location (home, work or school etc) then I would advise to take it to a B&N store.
Nook Tablet has connectivity issues. I had to dumb down my wireless router to get it to connect to my wireless. Nook Tablet Tech Support was NO help ... I had to do a google search for advice. It appears that Nook Tech Support won't help you adjust your router settings and suggests you contact your "ISP" provider. They want additonal Tech Support Fees to help you since your internet service is already running and it's a "hardware" issue. If I could take it back and buy a Kindle Fire ... that's what I would do immediately. DON'T buy a NT. I love me Nook Color Reader but would never buy a Nook Tablet.