Error: "This iPhone is supervised by another computer and cannot be used with this computer."

You may see this message when plugging a managed iOS device into a computer: 

"This iPhone is supervised by another computer and cannot be used with this computer.”

This means that device has been configured to prevent host-pairing, meaning that it cannot be plugged into another computer to be managed or make changes.

There are multiple levels at which host-pairing can be allowed/disallowed. In order for a managed device to be able to pair with another computer, the following must be true:

  1. The "Allow host pairing" setting within a Restrictions configuration profile is checked.
  2. If the device was enrolled in MDM using Apple DEP, "Allow pairing with macOS computers" must be checked within the DEP Account Settings in MDM at the time the device was enrolled.
  3. If the device was supervised using Apple Configurator, "Allow devices to pair with other computers" must have been checked on the 'Prepare Devices' screen in Configurator.

If any one of these options are not configured to allow pairing, then the device will not be able to be used with other computers. Additionally, Apple Configurator settings and DEP settings are only applied to devices at the time they are prepared and enrolled. To apply any changes to these settings, you will need to re-enroll the device.