Did you update from Beta to Stable, if so try the following.
Delete the data and cache of downloads app and download manager. This mught fix the problem.
Q: How to access the downloads and download manager app?
A:
Step 1: Unlock your phone.
Step 2: Open app drawer and locate settings app / bring down the QS panel and click on the gear icon.
Step 3: Click on the search tab on top of the settings app.
Step 4: Type "downloads" and then click on the app. Clear it's cache and storage which is under the storage tab.
Step 5: Type "download manager" and then click on the app. Clear it's cache and storage which is under the storage tab.
