Thanks for your clarification. I did input the correct Case ID or DOS Case ID , according to my "Immigrant Data Summary" sheet attached to my immigration package (which I have been using for the past twenty years of my family's immigration application process). In fact, I tried multiple websites under USCIS; I cannot proceed. Under Crazy Cat's suggestion, I tried again with only the A-Number; without entering the next "DOS case ID," nothing prompted. However, once I input "HNK" without the following 10 digits under the "DOS case ID". The system alerts with the above-mentioned message.
In fact, I tried to send feedback/messages via "https://www.usvisascheduling.com," which was previously my only way of contact for my immigration process. No response. My relative also tried to call the 800 number of the USCIS contact center. It's also another dead end.
Under the "USCIS IMMIGRANT FEE" advice sheet received after the interview (as attached), it advises me to go to "https://my.uscis.gov/uscis-immigrant-fee," but it shows a "404 Error" and "Sorry, we cannot find the requested page." My relative tried the same link in the US and got the same 404 Error page. Then, we click the suggested "Go to the myUSCIS homepage." and send the problem to "How to contact us for technical support."The email replied with the standard message on "Tips on Finding Your A-Number and DOS Case ID", and I am sure I did everything as advised with the correct input of numbers received. I am so worried that I will be banned at the POE if I have not paid the immigrant fee before traveling to the US, as it is bold in the payment advice sheet that "You must pay before you travel to the United States." Since I am a follow-to-joint case, I will enter the US or arrive at the POE alone.
USCIS immigrant fee.PDF