Same thing happened to me. After talking with an Xfinity person who couldn't help (she admitted after I was on the line with her for about 30 minutes that she worked in billing not technical services), I called mlb.tv (866-800-1275). I spoke with two women on the first day, who also couldn't help but the second one said this was a known problem on their end and it was "escalated to priority level". I called again the next day, and after speaking with one man and expressing my displeasure, I was transferred to a supervisor. I told him I was unhappy with not getting everything I'd paid for, and somehow he activated my mlb.tv account. So if you pester them enough, they may do the same for you.
