NOTE: If none of the following work to resolve the problem, since the tablet is brand new, I would suggest taking it back and getting them to exchange it for another one.
1. Try and restart the tablet. Sometimes it is that simple.
2. Update the firmware and any apps that need updating on the tablet.
3. If the problem persists, check your time and date on the tablet to make sure it is correct.
4. Should none of the former work...
a. Clear out the WiFi data on the tablet.
b. Reboot the modem/router.
c. Once the modem/router is fully 'up' again, reboot the tablet and re-input the WiFi data.
5. Check your internet connection. It may be what is going in and out rather than the tablet.
6. Make sure you have "Data" turned off on the device when using "WiFi" (that is if you have a plan with data through your tablet). If you don't make sure it is turned off, the device can keep trying to switch to "Data" when you try and use "WiFi".