The attendee does not have the recording shared with them in the recorder's OneDrive file. This is likely because the attendee didn't actually attend, but was only invited. To my knowledge only those who actually join the meeting are automatically provisioned with "Read" access on the video link in OneDrive.
Either have the recorder or a SharePoint Admin go into the recorder's OneDrive, select the video in OneDrive in the "Recordings" folder, and click "Manage Access" from the ellipsis menu. From there the list of users w/ permissions can be edited.
