Yet another problem with "Object reference not set to an instance of an object"

Hi,

 

Guess what - trying to translate an excel document through SDL Trados (Studio 2017) and it wouldn't let me export the finished document into excel. The document does not appear to be named any differently to other ones I have been working on recently. I created a new name for the file and tried to create a new document using the stored data. The same error message is appearing. Furthermore, the first document I created no longer opens. Any suggestions?

 

Eleanor