Try turning off Bluetooth and rebooting the tablet. While it is rebooting turn off the device you are trying pair with. Once the tablet has finished restarting the go back into the settings and return Bluetooth on. Once it is working, then turn on the device you are trying to pair with.
If it won't work with that device, then I would suggest trying that device with another tablet, phone or laptop to see if the device will connect. If it does, then the problem is from the tablet. You should also try pairing something else with the tablet. If it works, then the problem is the device you have been trying to pair with.