How do I get Glip permissions added to my app?

The Glip permission is replaced by the TeamMessaging permission. And you cannot change the permission of your app in production. You need to clone the app and change the app settings including the permission, then test and graduate the new app.

I have TeamMessaging permission.

When calling:

https://platform.ringcentral.com/restapi/v1.0/glip/data-export'

I received a 403 Forbidden error:

{
    "errors": [
        {
            "errorCode": "GIC-012",
            "message": "The requester must have permission to data export."
        }
    ]
}

This is not an app permission issue. It is a user permission issue. You need to authenticate the app with a super admin user.

As far as I know, the account is SuperAdmin, I can do everything else. How would I check the permissions?

Are you on sandbox? If you are, there is a current issue to set the permission to a super admin. But, I think the main super admin (normally in sandbox is the 101 if you have not changed the extension number) will have the permission by default.

If you are in the production, check this from the RC app.