Issue just appeared for me yesterday though I don't play via Geforce Now but via Steam.
Setting the DNS manually and flushing the DNS didn't help, still having the issue. As of yet I still can't access the game.
So annoying, all the more because this issue happened out of absolutely nowhere since I've been playing Warframe for months without issues.
One hint of solution could come from the fact that the only thing that changed on my computer recently was the batch of WIndows updates I downloaded & installed yesterday... Windows is known for their disastrous updates, maybe one of them may have caused havok? I'm not proficient enough to dig into that direction but maybe someone more gifted than I am could...
