The downloads might fail to be completed giving you a clock symbol if
a. there is no sufficient storage space in your device
b. due to unstable internet connectivity
If you are however using an internal memory and getting the error, try clearing either the app cache from your phone settings or re-install the app from play-store and retry.
Also try downloading content with a different internet connectivity
If you still continue to face the issue, please initiate a chat with us sharing a screenshot of your storage availability.