Melissa, this is the same response as for the post you placed on the LabVIEW board.
So I found the error, the component database the flag used to indicate whether a component belongs to a particular tier or not is incorrectly set in that component, the MCT6, according to our datasheet it is supposed to be included in the Student Edition. I will report this immediately to R&D, but in the meantime... I created a new component for you, its the same component but you should be able to add it to your user database.
Download the attached PRZ file, open Multisim, and go to File >> Open, point to this file, it will prompt you to add it to your user database, accept all the default questions and click Start, once its done, exit the dialog. Your component should appear on Place >> Component... select User Database... I think I configured it to be on the same place... Misc >> OPTOCOUPLERS... check it out.