Issue | Reason | Resolution
When attempting to open an Excel file from an email attachment or Windows Explorer, only the Excel application shell opens, forcing you to open each file directly within the application itself. You may have also received an error message stating "There was a problem sending the command to the program".
Dynamic Data Exchange (DDE) settings need to be updated.
Start Excel >> Office button >> Excel Options >> Advance >> In General Section check box "Ignore other applications that use Dynamic Data Exchange (DDE)"