cannot upload common images types

Multiple times over the past several weeks, I have experienced multiple failures using Adobe Express in Chrome on my Macbook, running both in-browser and as a browser supported app. One issue that has resurfaced multiple times is the failure of images to upload from my device. I am warned that these are not standard file types, but I know for sure that they are jpegs or PNG files. I empty my cache and restart to no avail. What is going on?