[Resolved] D455 RGB "No Frames Received"

We purchased 2x D455 units. One of them works fine, the other persistently reports "No Frames Received" on the RGB stream. On that one the Depth and IMU work fine.

Things we have tried:

1. Swapped USB cables (with the working one). USB icon (always) reports "3.2".
2. Different USB port (same PC)
3. Different PC
4. Upgraded SDK to 2.40
5. Upgraded firmware to 5.12.10.0
6. Ran the RGB by itself (all test cases) -- no IMU, no Depth, no Post-Processing
7. Varied frame resolutions and frame rates
8. Used both RealSense Viewer (2.36, 2.40, 2.41) and rs-capture. The Viewer reports no Errors or Warnings. rs-capture just quits after a few seconds.
9. Ran CustomRW -g to reset to factory settings.

The PCs used are all Win10 Pro.

I'm coming to the conclusion that there's just something wrong with this unit. How do we request a replacement? They were purchased through Mouser.

Thank you for any suggestions.