// Always check before calling open()
if (!AssessmentPortal.isOpen()) {
  AssessmentPortal.open({ token, onDone, onClose, onError });
}

function RecruiterDashboard() {
  const [portalOpen, setPortalOpen] = useState(false);

  async function startAssessment() {
    // ... get token ...
    AssessmentPortal.open({
      token,
      onDone:  () => setPortalOpen(false),
      onClose: () => setPortalOpen(false),
    });
    setPortalOpen(true);
  }

  return (
    <>
      {portalOpen && <AssessmentInProgressBanner />}
      <button onClick={startAssessment} disabled={portalOpen}>
        Start Assessment
      </button>
    </>
  );
}

true

false