People block for several reasons, sometimes obvious and sometimes not. In cases like yours where you and the other person we're getting along great then you were blocked for apparently no reason, I cannot help but think maybe somebody is trying to hide their online activity from a spouse or whoever. Or there is a slight chance that one of their other friends insisted they block you. I know that's kind of BS that people do that. But I'm more inclined to believe that somebody's just trying to hide their online activity