Weeeell, I'm going for a Sociology PhD, which isn't social psychology, but is similar. I know in Soc, early decisions come in Jan-early Feb, with the rest (most) coming in late Feb to March. April is rare, too, but common if you're waitlisted. I don't think it's too unusual. Maybe wait until the end of February (at least), then reach out? Have you checked on here to see when the program has started releasing decisions historically?
Again, I'm not social psych, but I wouldn't lose hope yet.
And yet, I say that, and I'm losing hope. I haven't heard back from most of my universities, although I've been waitlisted for one. I wish you the best of luck!