Hello Mom and all,
I submitted my I-485 package early May and received the copied package back late May with an I-797C notice stating my case was rejected. However, the reason for rejection was not noted anywhere on the notice. It says "Please refer to the accompanying notice (Form M-180) for further information" but such a form was not included anywhere in the package. There was just one green sheet stating "you are invited to resubmit your application package after you have corrected the reasons for the rejection" - which of course does not state the reason.
I've called USCIS but they did not have any information regarding the reason for the rejection. I also emailed Lockbox but have not heard back in over a week. I have gone through both the spreadsheet and the official USCIS instruction to make sure nothing is missing, to the best of my knowledge.
The only thing I could do now, before my medical exam expires past 60 days, is resubmit a new I-485 with a letter describing the fact above..... I wanted to see if you happen to have seen a similar instance or have an idea for a better action. Thank you so much.