Bluetooth issue

If you can't connect to one of these devices

• Get help connecting your iOS device and your car stereo.
• Learn how to set up your AirPods.

To get help pairing a Bluetooth accessory—like a wireless keyboard—to your iOS device, try these steps:

1. On your iOS device, go to Settings > Bluetooth and make sure that Bluetooth is on. If you can't turn on Bluetooth or you see a spinning gear, restart your iPhone, iPad, or iPod touch. Then try to pair and connect it again.
2. Make sure that your Bluetooth accessory and iOS device are close to each other.
3. Turn your Bluetooth accessory off and back on again.
4. Make sure that your Bluetooth accessory is on and fully charged or connected to power. If your accessory uses batteries, see if they need to be replaced.

If you still can't pair or connect your Bluetooth accessory

1. If you previously connected your Bluetooth accessory to your iOS device, unpair the accessory, put it back in discovery mode, then try to pair and connect it again.
2. If you can pair your accessory with some devices but not your iOS device, unpair the accessory from your other devices. Then try to pair with your iOS device again.
3. Check with the accessory manufacturer to make sure that your accessory supports your iOS device.
4. If you still have any of these issues, contact Apple Support: 

• • You can’t turn on Bluetooth or the setting is grayed out.
  • You can’t connect any Bluetooth accessories with your device.
  • The accessory manufacturer confirmed that your accessory is working correctly.

https://support.apple.com/en-in/HT201205