Replaced the cable. Now the screen doesn't work. What could it be?
If all of your devices in the Thunderbolt "chain" are still functional including your Cinema display at the end of it all, chances are there is a problem with the connectors that go from the logic board in the Thunderbolt display to the display panel itself.

It's a quite common occurrence that when you disassemble this, that the connector comes loose.  Look to make sure that the LVDS and power connectors are securely attached at both the logic board side and on the display panel itself.