I-485 case status online

I am not able to check I-485 case status online for the past few weeks. I was able to check the I-485 case status online two months ago.

However, I am able to check I-131 and I-130 case status online right now with no problem. All of the cases are submitted at the same time in Feb. 

Below's the error message I received after I typed the case number on USCIS website. I am wondering if anyone has the same issue. Thanks!

Validation Error(s)
You must correct the following error(s) before proceeding:

• My Case Status does not recognize the receipt number entered. Please check your receipt number and try again. If you need further assistance, please call the USCIS Contact Center at 1-800-375-5283.