It is not a channel mapping issue. 412-24 is where I get NESN. The regional sports channels are supposed to be hidden from those who do not subscribe to them, which is why it would not show up on your All Channels list. So, it is clearly an authorization issue. For whatever reason, Dish's system thinks that you do not subscribe to that channel, which is why you do not see it.I personally think it's a channel mapping issue.
James Long Uplink Activity page show it at 434, but should be mapped down to 412-24 (where I've had it in the past)
It also shows MASN at 432, mapped down to 412-22, and 412-22 is where I get it.