Look at `playNotificationSound`:
```javascript
  const playNotificationSound = () => {
    if (currentUser?.sound_enabled !== false && audioRef.current) {
      // Reset time to 0 to allow rapid replays
      audioRef.current.currentTime = 0;
      const playPromise = audioRef.current.play();
```
Is `currentUser` loaded when `loadNotifications` fires for the first time after `isInitialLoadRef` is false?
Yes, `useEffect` calls `fetchCurrentUser()`, which sets `currentUser`.

Wait. `setInterval` uses a closure over the state!
```javascript
  useEffect(() => {
    fetchCurrentUser();
    loadNotifications();
    const interval = setInterval(loadNotifications, 10000);
    return () => clearInterval(interval);
  }, [navigate]);
```
Oh my god. The `setInterval` callback `loadNotifications` captures the *initial* state variables, including `currentUser`, which is `null` on the first render!
If `currentUser` is `null` inside the closure, `currentUser?.sound_enabled !== false` evaluates to `true !== false` which is `true`. So that's not blocking it.
BUT `audioRef.current` might not have been rendered yet? No, `audioRef` is a ref, so it mutates in place. The closure always sees the latest `audioRef.current`.

So why does it fail or not play? 
Is the browser policy blocking it silently without logging?
Let's add a robust, standalone Audio approach that doesn't rely on the DOM tag if it fails, or maybe just force a click handler to "unlock" the audio context.