When you use this product, it’s possible that your Mac OS laptop only allows one-monitor display, especially when your Mac OS wakes up after sleeping mode.
After we have confirmed with Apple, we realize that the display issue is probably caused by the Mac graphics card. At the moment, the graphics card team of APPLE is investigating this issue; therefore, we suggest that our customers buy UTD21 dock for Windows only for the time being (Please be noted that the Thunderbolt ports of Windows-based laptop must support double video output; otherwise, the one-monitor display issue still exists).
Lastly, please follow our update on the MAC OS compatibility problem. Sorry for the inconvenience, and thank you for your understanding!