This issue can be caused by insufficient disk space, if there is no space left on the drive. In this guide, we will first check the disk space available, if there is no disk space then obviously you will need to free up some space if there is space then you follow the method below:
Check if there is sufficient disk space
1. To do this, Open Finder and Ctrl + Click or Right Click your Hard Drive from the left pane.
2. Select “Get Info” and see how much disk space is available.
look at the capacity and available fields to see how much is left of what. If there is disk space left, more then the file you’re trying to download then, proceed with the steps below:
3. Exit out of Safari and go to your Home Folder.
4. Ctrl + Click or Right Click your downloads folder and select Get Info.
5. Locate the Sharing & Permissions section and look under it. You may need to click on it to expand it.
6. If the padlock is locked, then click on it to unlock it. It may need your mac os x password, so if it asks you for the password, enter it.
7. This should show your name or username, this indicates that you as the user have permissions to this folder. If you do not see your name or username, then click the + symbol.
8. Choose your username and select it.
9. Make sure it has read/write permissions next to your name, if it doesn’t have, then modify it by clicking on it.
10. Hit the icon which looks like the cog and then select “apply to enclosed items”
11. Confirm the changes, and click the pad lock to lock the changes.
12. Once done, re-open Safari and test.