Netflix says 'There's a problem'
If you get the error code E121 or this message:
There's a problem
You seem to be using a VPN or proxy. Please turn off any of these services and try again.
It means that you're on an ad-supported Netflix experience and likely connected to Netflix through a VPN or proxy service, which isn't supported for this plan.
Note: If you don't have an ad-supported plan, follow these steps instead.
To fix the problem: