I have an iphone 12 mini. I used to pair it with macbook and other devices. Suddenly the bluetooth of the iphone doesn't connect to any devise. It cannot find any device to pair. Any idea?

That has nothing to do with pairing it with a Mac, which is not supported.

Make sure the device you want to pair it with is in discoverable (pairing) mode.

G_blu wrote:

I need to pair my iPhone 12 to headphones JBL

OK … I see no reference to a Mac in this request.

Therefore:

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

G_blu wrote:

I used to pair it with MacBook …

Nope. Apple devices like that don’t pair.

Tell us what you’re trying to do instead of how you’re trying to do it.