Can not find Differential application

I found that there is not exist the differential application.

I wonder if is this reason that make the arc diff fail.
According to the call logs, it seems that the differential.query API is not avaibale.
By the way,I was already an admin.

It’s probably uninstalled; use the query in /applications/ to list uninstalled apps, and then install it.

well, I had tried it yet, but could not find it.

I wonder if it is the config phabricator.application-settings that hidden this application and API function.

{
  "PHID-APPS-PhabricatorDiffusionApplication": {
    "policy": {
      "diffusion.default.view": "admin"
    }
  },
  "PHID-APPS-PhabricatorDifferentialApplication": {
    "policy": {
      "view": "PHID-PROJ-xxxxxxxxxxxxxxxxx",
      "differential.default.view": "users"
    }
  }
}

Yeah, looks like it’s only visible to members of the project PHID-PROJ-xxxxxxxxxxxxxxxxx.

Admins in Phabricator are do not bypass policies; If you’re not a member of that project, you won’t see it.