Good to know I'm not alone!

I did some research on USCIS website and figured the reason behind this is MSC or National Benefit Center is not one of the four USCIS Service Centers. And only cases filed with one of the four service centers can check status online using the receipt number. The Chicago lockbox facility uses another system for data entry. I guess it may take a while to combine their data entry with those entered in the main service centers.