Hi, I ran into the same problem a few weeks ago. Went to Service Canada, they told me my profile was "flagged" but couldn't tell me why. I went back home and called CIC, they told me my profile hadn't updated yet. I went back to Service Canada the next week, same problem. This time I had somebody helpful on the line, telling me something went wrong during my landing (computer or CBSA officer error, not clear which one) and I had to go back to port of entry. After another phone call to CBSA, turned out I could just go to a CBSA office, where they then properly "landed" me. Went from that office straight to Service Canada and obtained my SIN.
Do not wait until your PR Card arrives because something might have gone wrong during your landing too. Keep calling CIC until you get somebody helpful on the phone who can tell you exactly what the problem is. Otherwise you will have waited for months for nothing.