This rejection relates to the student loan section of the return where you have completed the box for the student loan plan type but not ticked to say that there is a student loan.

To amend this, if you open the return and go to the student loan plan section of the form and either tick box 1 to say there is a student loan, or if not applicable remove the student loan plan type box. Once done rerun your tax computation and refile to HMRC.