Just a couple notes on this I'd like to mention.
First, I gave up on FSD3 because the team who developed it has all but left the scene, and cover downloading has been on and off for awhile. I use Aurora pretty much exclusively now. Not as pretty IMO, but they still do updates and it will self update when a new version is released and you have a good connection to the webz. It's 0.4b I think right now
Second, DinohScene is right. If this person is telling you covers can't be downloaded from the webz, they either gave you a "not fully functioning" console and are trying to cover themselves or they aren't familiar with the cover download process.
There are some things you should check though. First I would open up Dashlaunch(you should be on 3.15) and see what your settings are. Write them down or save settings to a USB stick. Then go to settings and select restore to default settings. This will make sure your settings are where they need to be for internet access to be enabled and live access blocked. This time save settings to hdd1. Power down and boot back up. If you had your default path set to FSD or Aurora, you will not any longer go directly to them at boot up. Now you will go to NXE dash(microsofts off dash). As long as Dashlaunch is configured in the default settings, you can actually use the "test connection" part of the official dash network settings to see if you're connecting to the network without any fear of making it through to Live. This could at least help you determine if you have a network problem. If it doesn't connect, try a different Ethernet cord. If that doesn't work, see if you can find a network adapter you can borrow and try connecting wirelessly. This is where I would start. Good Luck!!