mmmmm, same thing here, error 401 and 601. Also, i can't even buy crysta, even with my paypal account.
Region: Americas
Country: USA
possible problem: i'm in Mexico right now trying to pay my first sub... I think i need to get back to the US, register my CC and select sub then proceed with my living in Mexico.

At least thats what I think is the problem. Why i think that?

Some months ago I got the same problem buying games and DLC from STEAM, exactly the same issue... and was resolved by traveling back to the US. Then some weeks ago, STEAM gave me a "special" URL to type in my browser every time I needed to buy things from the STEAM Store while being in Mexico, and it works every time.

I wish SE could make that "special" URL or make another workaround for this to be solved.

BTW, I'm still waiting a response from SE customer service...

Oh, and I bought the collector edition (if that matters)