Wait until tomorrow, the launcher may just work fine again.
Use a shortcut to the eso64.exe
Btw, the Play button does not show up until the launcher vets the game version using the patch manifest process. 99.99999999% of the time Manifest issues are meaningless. Unless you know it is a patch day.
 I was having the same or similar error — could not download patch manifest and so no “Play” button, only news and ad scroll.
 I was having the same or similar error — could not download patch manifest and so no “Play” button, only news and ad scroll.