"Preview as admin" returns Page Not Found

I have some pages which are only accessible to users who are part of a group. Since upgrading to CS-Cart v3, if I edit that page and click either “Preview” or “Preview as admin”, I get a 404 Page Not Found error.

However, if I do “Act on behalf of” on a user who is part of the group, then I’m able to access the page.

How can I fix that issue and give myself access to the pages?