You should be able to go to that course and see the Learning Mastery Gradebook when you show those concluded enrollments. Unless your IT department is doing something, those results are still available. Without more details, this seems like a local problem rather than with Canvas itself (we go back to previous semesters frequently).
You can check a student report (which is really bad, but okay in a pinch) by going to People > Student Name > Outcomes Report. It's a giant list, but it should have all Outcome results from any class that has them imported. The API will let you pull data, but that's a little more involved to get into something usable.
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