When you download your gradebook from Learn, the PeopleSoft ID is not formatted to upload to PeopleSoft. Some work needs to be done in the gradebook download to be able to upload final grades into PeopleSoft.
Step 1: Download Gradebook
1. Download the gradebook from Grade Center.
2. Delete all columns except for the Student ID (PSID) column and the grade you want to upload.
Step 2: Add leading 0
1. With the Student ID column selected, right click and select Format Cells.
2. In the Number tab > Category, click Custom.
3. In the Type field, delete General and enter seven 0: 0000000
4. Click OK. The leading zero will be added to all PSIDs.
5. Save the file as .csv and upload into PeopleSoft.
Original post can be found here