My headphones will not connect through bluetooth. What is wrong?

My headphones will not connect through bluetooth. What is wrong?

I go to connect the headphones via bluetooth and they show up in visible devices but they do not connect .

ANSWERS:

When pairing with Bluetooth it can’t connect when it is currently connected with something else so maybe you have some other device that auto connected it would be impossible for it to then connect to another so just disconnect from that device