I was trying to update my SCCM environment from 1602 to 1606 , I can see the hotfix got stuck while downloading.
How we can fix it ?
The solution seems to be straight forward , I stop/start SMS_EXECUTIVE service and it fixed the issue.
Within a few minutes, you will see the latest update appear and start to download.
Note : If the issue still persists try to have a look on log file dmpdownload.log.