Just my experience, and common sense. I do not know the exact method, however since these flexible IP address providers exist - maybe not even connected to them -, or how the English calls that (they change your IP automatically time by time), it looks like, based on that, you are virtually located in one region, so if you use the same virtually located VPN area, they accept it - I guess you use completely different VPN IP addresses for BOL and SB, even if not and you registered through VPN -, if not then you can't login. I do not remember exactly, just read about it, the first 1 or 2 part of the IP should count. (I read about it, because I had similar case in a given site, where I used a VPN, and I have choosen the same 'city, server', however I could not always login, I had to verify my account again and again, as they wrote I login from different location, so I just recognized the choosen 'city' in the VPN platform provides 2 completly different IP number type. (You know, the old binary based, and the new hexadecimal based.) After I verified my location again, and wanted to log back in, I was reconnecting again and again in the VPN until I haven't got the same IP number start till the 2nd point (.), so I could log in without an other verification, because this virtual locator - I don't know how they call it - identify my IP from the same area.) Maybe you registered on BOL with a different one, and they have some built in sub-program, what identifies it incorrect, so maybe it can be a reason why you get the network error message...
By the way, maybe for downloads it is okay, or reach restricted sites in your region, but for me this VPN thing looks like a bit fool around for a nice money, as obviously they can track you through that one, too, not a black magic, single individual can do it, if he wants... so they just sell another illusion. I used only free ones, and I really don't see the point to pay for any.