The signing rights under Mobilities OLA 3.0 are reserved for staff accounts as indicated in the list of users in "Accounts and Access" menu option. Please also make sure that your account has the “Managing students” permission enabled in the "Accounts and Access" set-up (which is different from "Viewing students" that allows accessing the student's lists, but does not allow signing). You can verify it via the "My Settings" menu option. If that is not the case - please reach out to the main institutional account holder of your Higher Education Institution or the person managing staff accounts.
The main institutional account holders are not able to sign the Online Learning Agreements. You can go here for more information on staff accounts.