1. Go to "Start" and in the search box type "msconfig". (Without the quotes.)
2. Next click the "Services" Tab.
3. Now scroll and find any services related to Bluetooth.
4. If any of them are 'unchecked' make sure you check them. If they aren't checked, they aren't enabled and won't load when Windows starts up.
Now if it is enabled, then it may well be the Bluetooth device you are trying to connect to that is the problem. Try connecting to a different device and see if it works. If it does, then you need to test the other device (the original one) on something else like a smart phone or tablet. If it can't connect to those either, the battery could need replacing or device may not be functioning correctly and need repair/replacing.