Possible Reason ...
Your input file could be saved as the Unicode text format that contains international character codes the ExpressConverter cannot recognize.

Correct:
  1. Open the input file with Microsoft Excel.
  2. Select Save as ... from the File menu to open a Save Window.
  3. Select Text (Tab delimited)(.txt) from the Save as type list at the bottom of the Save Window.
  4. Give a new file name if you want; otherwise replace your input file.
  5. Click OK button to close the window.
  6. Convert the input file.
You may want to know:
Convert files
mev file format