Only display on Thunderbolt works. Camera, audio and USB ports do not Very similar problem as this question, only the display itself is working on the thunderbolt monitor (I only have one, unlike the linked question which had two) with a MacBook Pro (Retina, 15-inch, Early 2013). No camera, no audio, no power to USB ports on the display. If I disconnect the thunderbolt display from the MBP, then power does go to the USB ports. 

OS X 10.10.5 (14F1509)

(more details below which probably don't amount to much)

This is actually the 2nd Thunderbolt monitor I've had recently. My company exchanged out my previous one, which had similar issues. The prior Thunderbolt was fine, then one day the display would not turn on, attached devices no longer received an active charge. Power would return to USB ports if display was unplugged from the MBP. Then a day or two later, everything went back to working, but the new monitor had already shipped out.

Replacement monitor worked fine the first day, then (of course) the day I shipped back the prior one, started acting consistently as described above - display only, no camera, audio or usb power. 

I tried the SMC reset steps (about three times, in case it was sensitive to pressing all 4 keys "at the same time" in just the right way). That hasn't worked.
There is a known similar issue with certain 27' Thunderbolt displays going black, and having connection issues. https://support.apple.com/en-us/HT204450 

Can you check the firmware version of the Thunderbolt display? 

Apple Menu > About this Mac > System Report > Thunderbolt (from left sidebar) > Thunderbolt Display. 

The latest firmware version should be 26.2 and the latest Port Micro Firmware Version should be 2.0.7.