It is not clear how exactly (U-Boot log) the Flash was programmed.
> After writing the image, and flipping SW3[7], we only get a steady
> power LED, and the two eTSEC2 LED rapidly blinking.
Why SW3[7]?
> The switch information references the upper 4 sectors or middle 4 sectors.
> Can someone clarify these addresses?
"middle" is a typo - should be "low".
Please refer to the P2020RDB-PCA Specification, 5.1 NOR Flash Memory.