Several of us got together last night and discovered the true cause of the issue. http://forums.elderscrollsonline.com/discussion/80209/found-the-root-cause-of-many-login-issues-with-workaround-for-error-209#latest
It was acknowledged by a ZOS rep in one of the threads in here, that's the best we've got for now. But at least, until they do fix it, there is an easy workaround we can use.
I tried the uninstall and reinstall and it didn't work. The launcher on my laptop has mysteriously started working but I did what they sent you anyway and about to try it on my desktop.I sent in a support request for error 209 by support tab on this site and I got a response pretty damn fast, was a bit surprised.
Granted this is a cut and paste response, but I personally have not seen this resolution on the forums so I'll share in the event it helps someone else
Response By Email (04/16/2014 12:08 PM)
Greetings LunaRae!
Thank you for contacting The Elder Scrolls Online Team regarding the 209 Patch Manifest Error you are receiving.
Please follow the steps that we have provided below to help assist with this issue:
1. Open your Launcher
2. Look at the top right hand corner for your Launcher for your Settings Option(looks like a gear icon)
3. Change Megaserver from NA to EU (or vice versa depending on which server you are usually on) and close out of the Launcher
4. Open the Launcher back up and go back to Settings and change the Megaserver back to the original server you had it on.
5. Again, close the Launcher.
6. Now once you open your Launcher back up, your issues should be resolved and/or the game launcher should allow you to again update your game.
If these steps have resolved your concerns and you are now able to play the game, or if your concerns are still existing and more research into your concern is need, please let us know and we will happily assist as needed.
You can find more information about The Elder Scrolls Online on our website and social channels (Facebook, Twitter, and Google+).
Thank you for your continued interest and support!
Warm Regards,
The Elder Scrolls Online Team
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Just as an FYI - I read their support article on Error 209 and it suggests that if a player is unable to remediate the 209 error after a repair THEY suggest you re-install the entire game. I strongly believe it might be a long time before any fix from Zenimax comes out, if it does. I'd encourage everyone to read the info available on these forums to work on solutions provided by other players. And of course, put in a support request! They provide support, you (may) pay for said support, so get it!