I replaced the combo cable, replaced the logic board. And Still...
The display does not work when I plug both the power cable and Thunderbolt cable into my Macbook Pro. However, if I plug a Tbolt cable from the Tbolt display to the MBPro, the display works as expected. I have also: Updated the firmware, did an NVRAM reset, did a SMC reset, checked all board connections multiple times, and the magsafe power plug works as expected. Any Ideas, folks?