Hi Greg,
May I know what is the file extension that you are trying to upload? The allowed default extension is as follow:
zip,txt,pdf,gz,php,doc,docx,ppt,xls
I just tried to upload some files on your site with extension .txt and .pdf and it seems like the upload went just fine from my end. Refer to my video link here,
https://take.ms/ebGTa.