Presumably you have tested to see that if one of the fields has new data entered into it via your FM application and then you re-export the file that you can see the new/additional data. If all you see is the new data, then there is one problem. If you still see the old data as well as the newly entered data the problem is slightly different. I have seen this once before where the data contained special characters like carriage returns or a combination of &?? that was then interpreted by the program to be ignored and all the special characters had to be removed from the original data before it was visible on the new system!
Or is it a simple thing like the colour of your text is the same as the colour as the input field and it appears not to be there because you can't see it, for example white on white?