Unable to upload small files allowed on the list of files that can be uploaded on Experts-Exchange?

I keep getting the error when trying to upload certain accepted file in EE. I have been struggling to get some files uploaded to EE but cannot due to the following errors.

The extension of one or more files in the archive is not in the list of allowed extensions: xl/worksheets/_rels/sheet1.xml.rels

Not sure why this is happening. The file comes from Google Sheets and is part of their download or export feature. I download it locally as an xlsx file then attempt to upload it to EE. It does not work. What am I doing wrong?
Fletcher BurdineTableau Trainer & Consultant Sales Exec.Asked:
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Fletcher BurdineTableau Trainer & Consultant Sales Exec.Author Commented:
I uploaded  the file. See original question.
Joe Winograd, Fellow&MVEDeveloperCommented:
Hi Fletcher,

You are not doing anything wrong. This is a bug in the EE uploader, and I've already submitted a bug report on it:
Upload of XLSX file fails

As you probably know, XLSX is really an archive file, and what seems to be happening is that the EE uploader finds a file inside the archive that is not in the list of allowed extensions. It doesn't happen on all XLSX files — just some. When it happens, a work-around is to save the file as XLS instead of XLSX, as XLS is not an archive format (and, of course, it is an allowed extension at EE). But note that Google Drive can download only in XLSX format (and DOCX) these days — it stopped support for downloading XLS (and DOC) years ago, so you'll need to convert it from XLSX to XLS with other software, such as Excel. Regards, Joe

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Kyle SantosCustomer RelationsCommented:
Hi Fletcher,

As Joe said, you're not doing anything wrong. His explanation is great and we'll investigate the issue.  

Joe, thank you for helping Fletcher!


Kyle Santos
Customer Relations
Joe Winograd, Fellow&MVEDeveloperCommented:
You're welcome, Kyle, and thanks to you and your team for investigating the issue. Regards, Joe
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