If you submit the paper of American College Students Mathematical Modeling Competition (MCM/ICM), but the system shows that you have not received it, there are several reasons:

1. System update delay: Due to the huge number of entries submitted, the system update may be delayed, so please be patient.

2. Submission failure: due to network problems or other unknown reasons, the submission of the work failed. Please try submitting again and make sure the network connection is stable.

3. No payment when submitting: If you encounter payment problems when submitting your work, your work will not be accepted by the system. Please check your payment record.

4. Return for revision: If the work violates the competition requirements or format specifications, it may be returned for revision, and it needs to be revised and resubmitted in time according to the feedback from the review.