I am trying to upload 2 zip files.  I have uploaded tons of these files, but now I’m getting this message: Zip file contains illegal contents

I looked at this blog to explore why: https://blogs.connectusers.com/connectsupport/content-fails-to-upload-to-connect-with-error-message-illegal-content/

Then I unzipped the file to see if any of the blocked executable extensions might be present.  I found none. 

I'm stumped at this point and don't know what to do.