Go to Start > Control Panel > Appearance > Folder Options, open the View tab and check the Hide extensions for known file types:
If this doesn't help, you can't do anything else because the software seems to be designed with this option. However, the fact that it displays the extension will not affect your projects. I recommend you contact the support team using
781-565-5000 phone number.
Note: If you apply the above steps, once you save the project, it will display the document using its name without the extension.