Sounds like you either have some drivers or firmware issue. Try to perform a manual firmware upgrade of the Bluetooth device. Run the following program: C:\dell\drivers
Apparently seems like your Bluetooth is either disabled from your network connections or may be there is some hard switch which turned off.
Other way is to check on your keyboard from top F1 to F12 keys if you can see a Antenna like sign on any of key then press that key by pressing Fn key together.
If the problem still persist then I would recommend you to go on your manufacturer`s website to download the latest driver and update your driver that might can help.