Document Cloud files not accessible on Kindle Fire 8: the document path is not valid

I am getting an error on my Kindle Fire 8: "the document path is not valid" after a long string of negative numbers under the progress bar. I have had a paid subscription for a long time and it is current. My files are accessible from other devices. I have deleted and/or uninstalled the app and/or turned my Fire off and back on, more than once, and that didn't help. It shows me my files but seems to think I'm not logged into Document Cloud when I try to open a file, whether the file is new or old. Even though it lists my Document Cloud documents, it offers me the opportunity to turn on Mobile Link but won't accept the login. So none of my Cloud files are accessible on my Fire. Please help.