I assume you are saying that when you use a Windows PC to access the web site that the docx file gets successfully downloaded to the Windows PC and Word can open it. So things are working fine on Windows.
What do you mean by "not working" on CentOS? Do you mean that nothing gets downloaded at all? Or does something get downloaded but its contents are not what you expected? Exactly what is the behavior you are seeing.
Also, which browser are you using on Windows and which on CentOS?
My guess is that it has something to do with the browser configuration. The only difference in the working case (Windows client) and non-working case (CentOS client) is that you are using a different browser. You might have to configure the browser on CentOS to recognize the mime type used for docx files and have the browser react correctly (that is, download the the file and place it on disk somewhere).