Cannot access my own files after e-mailing

Yesterday I scanned seven files using Adobe Scan on my iPhone and saved them as PDFs. I e-mailed six to myself (sent a link via Gmail), and one to a colleague. I do this all the time, and have never had a problem before.

My colleague was able to open and download her file, but when I tried to open my six files on my MacBook Pro, I got the following message:

"The files have been removed or you don't have access. Contact the document owner to request access."

I can still see and open all the files in Adobe Scan on my iPhone. What is going on? This method worked fine just a few days ago.