Google says to clear cache and data on Play Store and Download Manager when experiencing download problems. I can't find Download Manager on my Android device.
See if you have something like this:
System settings > Application Manager > All > Downloads
Steps to clear the cache of the Download manager app:
1.Open "Settings" - either:
a) pull down the top (right) menu and click the "cog" icon
b) click on "Application" and select "Settings".
2.Go to "Applications" then tap on "Manage Applications" (older versions)
Or "Application manager" (newer versions)
3.Select the "All" tab (to the right)
4.Now scroll down to the "Download Manager" app and tap it.
5.Tap on "Clear cache" and "Clear Data".
...all done.
In Android 9, go to Settings > Apps & Notifications > App Info. Select 3 dots in upper-right and Show System. Download Manger should show in list now.
On samsung galaxy, go to "apps," then click on the three dots in upper right corner. Select "show system apps." From there you should be able to find download manager. Go to "storage" then "clear cache."