Operation Not Completed
Sometimes when you attempt to download a mod, you will receive an error and "Operation Not Completed". This can mean one of several things.
Check Your Space First
The first thing to do is to check how much space you have used. Keep in mind that the website and in-game mod manager do not use the same units of measurement.
Bethesda Server Issues
If a mod is freshly updated, it may take a bit for it to propagate across the system. Wait about an hour if you see your favorite mod has just updated.
You've downloaded a mod with the same name as another mod. You've now got the old mod's archives taking up room in your reserve space, but the plugin file has been erased by the system. Now you cannot download anything else because you've hit the space limit of how much you can download. Skyrim players call this "Ghost Space".
Microsoft or PSN Server Issues
Server issues for PSN or Microsoft or your internet connection are receiving time outs. Check PSN or Microsoft or your internet connection.
Check your internet connection. Bethesda games are games as service and require a good internet connection. Wired connection will be the best way to connect online for online gaming.