Note 5 not downloading files.

[AC Question]

I download a pdf I need from my email every week and audio files from an app almost every day. The pdf used to show a pop-up with a downloading bar and automatically open the file when complete. Now that pop-up flashes briefly then vanishes and nothing opens and I cannot find the file anywhere.
When I download audio files from my app (its whole purpose is to stream or download business recordings) the download never starts and the app crashes after a few moments.