I agree with David. This is a technical issue that needs to be referred to info @ wikitree.com. No amount of mentoring can fix it.
Problems like this one crop on a frequent basis. It occurs to me that the Special:UploadGedcom page needs some text saying "If this report says GEDCOMpare Report: Complete but you can't see the GEDCOMpare file, send a message to ..."
And lest there be any confusion, it's not necessary to delete one Gedcom before uploading another one.