There are occasions when an user will have more than one account in Canvas. Sometimes they will have an account with the old SID and another account with a ctcLink. 
When this occurs, the Canvas Admin can merge the accounts into the ctcLink and retain the user's past course information. Here is the Canvas guide on How do I merge users in an account?
It is also possible that the user will have two ctcLink accounts. In this case, the Canvas Admin will need to contact Enrollmentservices@shoreline.edu and work with Enrollment Services to fix the user's ctcLink ID in ctcLink.