1. Locate the normal.dotm file in the user profile path: %userprofile%\AppData\Roaming\Microsoft\Templates\Normal.dotm
2. Rename the file name Normal.dotm as Normal_old.dotm
3. Now try to open the document again, this should fix the issue.
2. Rename the file name Normal.dotm as Normal_old.dotm
3. Now try to open the document again, this should fix the issue.