27" Cinema Display Black Screen after firmware update

Hi Guys.

Pulling my hair out a bit here.

I have a 27" LED cinema display which was all working great until i ran the latest firmware update now i have a black screen.

Everything is working on it i can use the isight camera & it also plays audio if i play a movie in iTunes .

I have tried attaching it to a few computers all with thunderbolt ports my iMac 27" my Macbook air & another macbook pro.

They all register the display has been attached & i can select in system preferences the display also flickers for a split second then remains black.

Is there any way to reset back to factory settings or try & force the firmware update to run again i have tried re running it but i just keep getting the display doesn't need this update message.

I have tried resetting pram I've also booted in safe mode & selecting a resolution as one or 2 had suggested to try on here.

I have looked at connections & all seem to be in order & no damage to any of the cables.

Any help would be greatly appreciated

Thank you