First of all, You should check your assignment status at the following link

https://admission.ignou.ac.in/changeadmdata/StatusAssignment.ASP

If it is showing not found then don't worry, because it takes around three to four Months to update your assignment status. If you have recently submitted You assignment then it may take around March to update Your assignment status.

If you have submitted long ago then also no need to worry Just show the receipt of your submission(if you have) to the study center coordinator and they will let You know.