Post system details please:

Apple icon (top left of menu bar) > About This Mac > More info…

Try shutting down you Mac, reboot router then reboot Mac.

Also worth ensuring the OS X Firewall is switched OFF during download and that any router firewall is not blocking it in some way.

System Preferences > Secuirty & Privacy > Firewall

This is in OS X 10.9 Mavericks, It may be slightly different in other versions.

Try again. If not try;

Renew DHCP

Network > Select the network you are connect to (indicated by green circle)> Click Advanced > Click renew DHCP lease

Try again. If not try;

Change DNS to public

Change your DNS settings to a public DNS server (non-ISP).

I used Google: 8.8.8.8, 8.8.4.4
On the Mac, to change the DNS server IP addresses go to:

System Preferences > Network > Advanced… > DNS

Note the existing ones usually automatically added by your ISP then change them for the Google ones of other you prefer. Remember to Apply changes after clicking OK when done.

Once you have tested you should set them back to previous setting (normally automatic via router for DNS when others removed)

They updated the list of ports that need to be open for ESO here. Worth doing to avoid issues at launch:

WHAT PORTS DO I NEED TO OPEN TO ACCESS THE GAME?
Updated 03/25/2014 08:07 PM Published 02/15/2013 07:46 PM


To best access The Elder Scrolls Online, players should configure their routers to open the following ports:

Ports 24100 through 24131
Ports 24500 through 24507