Any ideas on how to fix this?

uninstall and reinstall the client

209/210 – Patch Manifest Error

This error occurs when selecting the EU server. Users instructed to uninstall/reinstall client.

Please follow the steps below to uninstall and reinstall the ESO beta client (do not uninstall the game from your computer’s Control Panel):

Uninstall the game client
1. Select the Beta client on left hand side of the patcher
2. Go to game options
3. Select Uninstall

Install Beta Client
4. In the launcher Select the Beta client
5. Click Install

That's implying I'm willing to reinstall a 20 g file on to my computer for a second time

This does not always work, and has NOT worked in my case......