Thunderbolt Accessory Error | Mac-to-Mac USB Connection

If you're receiving a Thunderbolt Accessory Error, like the one below, while using a USB cable connection with Luna Display, there are a few workarounds that you can try to fix the issue. Usually, this error can point to an incompatible cable type or an incompatible Mac device. 

This message will show on the primary Mac's system when the USB cable is plugged into the primary device.

What are the requirements for using a USB connection in Mac-to-Mac mode? 

First, let's make sure your device and Luna applications meet the requirements needed in order to use this connection type. 

USB Mac-to-Mac support requires:

  • Luna applications:  Must be running Luna Version 5.3 or later
  • Mac: macOS 10.15 or later on both Secondary and Primary computers
  • A compatible USB cable:    
    • You will need either a USB-C to USB-C cable or USB-C to USB-A cable depending on how old your secondary Mac is
    • For Mac-to-Mac mode, we require USB-C cables that support at least USB v3.1 or later, but we recommend USB v3.2. When shopping for a cable look for one that lists support for v3.2 and mentions 20Gbps transfer with support for 4K @ 60hz video
Please note:
  • The USB-C cables from Apple that come with your iPad and Mac ARE NOT compatible with Mac-to-Mac mode – they are USB v2 cables while we require USB v3.1 or later.
  • USB hubs and adapters are also not compatible with Mac-to-Mac mode.

How do I get rid of the Thunderbolt Accessory Error? 

There are a few ways to prevent this error from showing on your Mac. Please try the following steps and see if they help: 

  • Make sure your USB cable meets the requirements listed above
    • If you're using a USB-A to USB-C cable, make sure the cable is capable of data transfer and is not registered as a "Power Only" cable
  • Unplug and replug the USB cable into compatible ports on your primary and secondary Mac devices
  • Do not plug the USB cable into any hubs or adapters - try plugging the USB cable directly into the computer's port
  • Fully power down both your primary and secondary Mac devices, reboot them, and try again
  • Try using another compatible USB cable to see if you receive the same error 
  • Update the macOS on your devices
  • If using an older Mac as primary and a newer Mac as secondary, attempt to use the newer Mac as primary and the older Mac as secondary 
    • For example, if you're using a Mid-2014 MacBook Pro as a primary device and an M1 iMac as a secondary device, try switching it up. Use the M1 iMac as your primary device and the Mid-2014 MacBook Pro as your secondary device and the USB cable should be recognized by the system
If none of the above steps work for you, it's possible that the cable you're using is not supported
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