Thunderbolt Accessory Error | Mac-to-Mac USB Connection

If you see a Thunderbolt Accessory Error while using a USB cable with Luna Display, it usually means the cable or Mac isn’t fully compatible. Below are some ways to fix it.

This message appears on the primary Mac when a USB cable is plugged in.

Requirements for USB Mac-to-Mac Mode

Make sure you meet these requirements for USB connections:

Luna apps running version 5.3 or later
Both Macs on macOS 10.15 or later
A compatible USB cable:
- USB-C to USB-C or USB-C to USB-A (depending on the Mac)
- Must be USB 3.1 or later (we recommend USB 3.2)
- Look for cables that say USB 3.2, 20Gbps, 4K @ 60Hz

Important:

Apple USB-C cables that come with your iPad or Mac do not work for Mac-to-Mac mode — they are only USB 2.0.
USB hubs and adapters are not supported.
For USB-C to USB-A cables, the USB-A side must be plugged into your secondary device.

How to Fix the Thunderbolt Accessory Error

Try these steps to fix or prevent the error:

Make sure your USB cable meets the requirements listed above.
- If using a USB-A to USB-C cable, confirm it supports data (not just power).
Unplug and replug the USB cable directly into both Macs (avoid hubs or adapters).
Restart both Macs fully, then reconnect the USB cable.
Test a different compatible USB cable.
Update macOS on both Macs.
If using an older Mac as primary and newer Mac as secondary, try switching them:
- Example: If using a Mid-2014 MacBook Pro as primary and an M1 iMac as secondary, swap them. Use the M1 iMac as primary and the MacBook as secondary.

If none of these steps work, the cable may not be compatible.