I just bought the iPhone 11pro today and my Bluetooth is not working. It won’t pair with my other devices. What can I do?

And just to verify, first you went to Settings/Bluetooth and observed the spinning circle. You put your fitbit into pairing mode and it did not appear in the Bluetooth screen on your phone. And you put your Bose speaker into pairing mode and likewise it did not appear in the Bluetooth screen in Settings. Did you also try factory resetting the fitbit and speaker, in case their pairing tables were full. IIRC, a Fitbit can only pair with one phone, so if it was already paired you can’t pair it with another device until you reset it (check the manual). The Bose speaker can pair with more than one device, but it has a limit (which I don’t recall).

If you have done all of the above troubleshooting take the phone and the devices to an Apple store for diagnosis. Make an appointment to avoid a long wait—>Genius Bar Reservation and Apple Support Options - Apple

Are you putting the devices into pairing mode?

See this Apple support article—>Pair a third-party Bluetooth accessory with your iPhone, iPad, or iPod touch - Apple Support