my macbook air is not recognizing my thunderbolt display

Hi we have a Thunderbolt display that will not recognize one of our MacBook Air. This started last week on this Macbook Air the other Macbook Airs work fine.

I do not see any settings to change to fix. Also the port in the Macbook Air in question looks fine. The cables when I plug in to other the power turns green and it stays amber on the one in question as if it is not recognizing the unit. Any help would be much appritiated.

Thanks