What license type did you give your student worker Mason? If you look at the Knowledge Base article here on License types, the student worker will not be able to access TDNext with a Client type license.
For your administrator Michelle, depending on what functions you need her to be able to do, you will need to add her as an organizational administrator. To do this, an existing admin with permissions to add other admins needs to go to the Admin application and select your BE. Then, select the Administrators tab and choose the "Add" button. Try that, along with the desired license type and see if she is able to access everything needed at that point.
Please let us know if you have any further questions or need assistance with configuring their permissions further.