Getting a Object Reference error in prod only when trying to use the Word DocumentClass

Question

I am writing a program that uses a .dotx template and does a merge of data in an aspx page. The program works perfect on my Dev workstation locally but when I deploy it to

Answer 1

After installing Office on the target machine, make sure you open one of the apps like Word directly because there may be more prompts for activating the license. The API won't work until you step through this process and the errors generated will not be clear as to what the problem really is.

The NullReferenceException may thus be caused by Word being unable to open the document, thereby Word.Documents.Open() would return null. To be honest I am not 100% sure this is what is causing your problem -- As I stated, the errors will not clearly tell you what the problem is. (I ran into this scenario myself a while ago and though I know the API was throwing an exception I cannot remember if it is the same as what you're seeing.)