iPhone isn't connecting to Bluetooth

Follow the instructions here:

If you can't connect a Bluetooth accessory to your iPhone or iPad - Apple Support

If they don't help, either make an appointment to have your phone examined:

Genius Bar Reservation and Apple Support Options - Apple

or contact Apple Support directly:

Contact - Official Apple Support

I'm having this same problem - trying to pair it with a fitbit, or my car, or a bluetooth mouse - no device is recognized by the phone. Bluetooth turned off and on; phone off and on and hard restart. Nothing.

Following the process as outlined for various devices that I’ve previously successfully paired, including a Fitbit luxe, my car’s Bluetooth connection, and wireless headphones. None show up as devices on the phone when they’re in the pairing mode. Not sure about the original poster.

In your case, I would suspect a hardware issue.

Genius Bar Reservation and Apple Support Options - Apple

What, exactly, are you attempting to pair it with?

You can not pair it with a computer or another phone or tablet.

What device are you pairing to and what process does the device require you to do to put it into pairing mode so that it is recognized by your iPhone?