What do you mean with 'FE application'? Are you talking about the File Explorer? That's the only reference I could find, but that's a component and not an application.
If it is a custom application, you will need to share more about it, since we can't look into your system. It probably has roles and you need to assign the roles to grant access. That's how it usually works, but it feels a bit simple to be the answer to your question.
Please mark any helpful or correct solutions as such. That helps others find their solutions.
Mark
