Your learner may have created an account separate from the OpenSesame Plus invitation they received. If this is the case, please have them log into the OpenSesame account they created. Next, have them open the OpenSesame Plus invitation again and click the email’s link. Then ave them refresh the page they are on. This should connect the accounts.
If a learner needs their OpenSesame Plus invitation resent you can reach out to OpenSesame support at email@example.com.