I used Hola with Mexico VPN on my mobile (free!) to sign up, I even had an existing League Pass account which I linked this to - just sign in after selecting Mexico VPN, the annual package, and applying the code. Otherwise you can create a new account.
Code SAVE10 came in my email and is for the NBA China Games, valid until October 8
PRESEASON10 code came in my email, expiry is unknown, it says "Our discount will only be available for a limited time, don't miss out on this special offer!"
Note that the Mexican Peso has dropped a little since this deal was posted with the SAVE10 code, so it's now about $92.50
Credit also to the original Mexico VPN deal.
I had the same issue. Clear your browser history from at least when you tried signing up (so you don't lose other cookies etc) and it should work. Worked for me.