Hi Melissa, 

Welcome to Box Community and glad to assist! 

Can you log in to box.com and in the All Files page, click the bell icon at the top right.

If the collaboration invite was sent in the account you're logged into, the collaboration notification will be posted there. And you can just click the collaboration notification and it should take you to the collaborated file/folder. 

Hope it works! 

What if the notification does not show up?