Collaborator unable to see form submissions

Hi guys, so we just recently launched a site for a client with a form file upload submissions that pings them an email once someone submits information and images. Now the client has been set up as a collaborator and when he clicks the link in his email to view the submitted content it says that he needs to log in to view. Now this works perfectly when signed in as the admin, but we need to allow a different email address access to those images. What do you guys think im doing wrong here? Thanks!

Here is my site Read-Only: LINK
(how to share your site Read-Only link)