Refer to the exhibit.

```json
{
  "name": "RLS Sales",
  "rules": [
    {
      "table": "Sales",
      "filterExpression": "[Region] = USERPRINCIPALNAME()"
    }
  ]
}
```

You apply the above RLS rule to a semantic model. The rule is intended to restrict sales data by the user's region, which is stored in the user's email domain (e.g., user@west.contoso.com). However, the rule does not filter any rows. What is the most likely issue?