https://codesandbox.io/s/upbeat-frost-3tt25

1. Press Suspend, see "Loading..."
2. Wait five seconds, you'll see "Happy birthday" at some point 
3. You won't see it again no matter how long you wait

Expected: you'll see it every five seconds.
workInProgress: Fiber,
  suspenseInstance: SuspenseInstance,
  renderExpirationTime: ExpirationTime,
): null | Fiber {
   
   
  if ((workInProgress.mode & BlockingMode) === NoMode) {
    if (__DEV__) {
      console.error(
        'Cannot hydrate Suspense in legacy mode. Switch from ' +
          'ReactDOM.hydrate(element, container) to ' +
          'ReactDOM.createBlockingRoot(container, { hydrate: true })' +
          '.render(element) or remove the Suspense components from ' +
          'the server rendered components.',
      );
    }