Excel and Libre Office both will not recognize my documents made using Axlsx

[colinm...@gmail.com]

So I create a document using Axlsx and it just a zip file that excel and Libre Office do not recognize as xlsx documents. When I try to open the document in Excel it says that the file format and extension do not match, but it is able to open the document and save it as a xlsx (which it recognizes as an xlsx) no problem.I was wondering what axlsx could be doing to cause this and how to fix it. I'm passing a workbook to different methods which could be what's causing the issue but I'm not sure.