Quick answer:
Incompatible cable: Must be USB 3.1+ with data transfer support
Wrong cable type: Apple iPad/Mac cables are USB 2.0 only (won't work)
Connection method: No hubs or adapters - direct connection only
System requirements: Both Macs need macOS 10.15+ and Luna 5.3+
⚠️ 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 restrictions:
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:
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.
Why doesn't my Apple USB cable work?
Why doesn't my Apple USB cable work?
❌ Cable limitation. Apple USB-C cables included with iPads and Macs are USB 2.0 only and don't support the data transfer speeds required for Mac-to-Mac mode.
✅ Solution: Purchase a USB 3.1+ cable that specifically mentions data transfer and high-speed capabilities.
❗Look for: Cables labeled USB 3.2, 20Gbps, or 4K @ 60Hz support to ensure compatibility.