How do I resurrect a Thunderbolt display?

I have had a similar issue a few weeks ago. In my case the screen was not "completely" black, but it was close. Going to the "Display" tab in the settings app and turning up the brightness did the trick.

However, it may also be an actual hardware failure if there is nothing at all visible on the screen. In that case you should take the display to an Authorized Apple Service center.

In the pulldown, select Mac repair since these require the same training, tools and skill to repair as an iMac does.

My Thunderbolt cable was recently diagnosed as the cause of a 'dark' display. Like you, I have basic secondary features -- such as the Thunderbolt display bridging my MacBook pro over to the LAN. So consider a) getting a new cable; b) wiping any dirt accumulation in the cable or interface.

I had this issue. For me the fix was to leave the display unplugged from the power for a few minutes. It came back to life after that. I did also blow into the cable in case there was dust inside. The PRAM reset had no effect

Black screen issue resolved... I purchased a fully working and tested used Thunderbolt monitor yesterday. Everything worked fine at the store when tested on a MBP that is identical to my own.

At home, the screen would not come to life and remained black even though it was available in System Preferences. I could also mouse over to the black screen. So clearly it was recognized, just no display.

After trying a new Thunderbolt cable, resetting PRAM, restarting my MBP multiple times and unplugging and plugging in the Tbolt cable (original and the new one) with no luck, I plugged the power directly into the wall. The screen flickered a bit so I knew I was onto something. A few more times switching between wall power and surge protector and the display finally came to life. I have the Thunderbolt plugged directly into the wall now which is not ideal, but hey - at least it works.

So, not exactly steps you can follow directly, but it does prove that these monitors are glitchy but can be resurrected. Frustrating! At least I'm in business now and I hope you're as lucky.