You're right, your Bluetooth settings look fine. You said that the printers show the same error. What is the error message?
Also, just to cover all the possibilities, are you sure these printers aren't already paired to a device?
Lastly, you could try double checking a Bluetooth radio is installed on the printer by sending this command through Zebra Setup Utilities:
! U1 getvar "device.bluetooth_installed"
It should return yes if the connected printer has a Bluetooth radio installed.