diff --git a/app.py b/app.py
index 0e5df86..2df65cb 100644
--- a/app.py
+++ b/app.py
@@ -132,21 +132,30 @@ class FlicButtonHandler:
             logger.error(f"Error saving subscriptions: {e}")
 
     async def send_push_notification(self, subscription: Dict, message: str):
-        """Send a web push notification."""
+        """Send a web push notification with proper key handling."""
         try:
             if not self.subscriptions:
                 logger.warning("No subscriptions available")
                 return
 
+            # Debug output
+            logger.debug(f"Using VAPID key: {self.vapid_private_key[:50]}...")
+            logger.debug(f"Subscription endpoint: {subscription['endpoint'][:50]}...")
+
             webpush(
                 subscription_info=subscription,
                 data=message,
                 vapid_private_key=self.vapid_private_key,
-                vapid_claims={"sub": "mailto:your-email@example.com"}
+                vapid_claims={
+                    "sub": os.getenv('VAPID_CLAIM_EMAIL', 'mailto:your-email@example.com'),
+                    "aud": subscription['endpoint'].split('/send/')[0] + "/"
+                }
             )
+            logger.info("Push notification sent successfully")
         except WebPushException as e:
-            logger.error(f"Push notification error: {e}")
-            # Remove invalid subscription
+            logger.error(f"Push notification error: {str(e)}")
+            if 'Invalid JWT' in str(e):
+                logger.error("VAPID key validation failed - check key format")
             self.subscriptions = [s for s in self.subscriptions if s != subscription]
             self.save_subscriptions()
 
@@ -169,16 +178,20 @@ class FlicButtonHandler:
         await self.broadcast_notification(message)
 
     async def broadcast_notification(self, message: str):
-        """Broadcast notification to all subscriptions."""
+        """Broadcast notification to all subscriptions with error handling."""
         if not self.subscriptions:
             logger.warning("No subscriptions to broadcast to")
             return
 
-        tasks = [
-            self.send_push_notification(subscription, message)
-            for subscription in self.subscriptions
-        ]
-        await asyncio.gather(*tasks)
+        success_count = 0
+        for subscription in self.subscriptions:
+            try:
+                await self.send_push_notification(subscription, message)
+                success_count += 1
+            except Exception as e:
+                logger.error(f"Failed to send to {subscription['endpoint'][:30]}...: {str(e)}")
+
+        logger.info(f"Notifications sent: {success_count}/{len(self.subscriptions)}")
 
     async def handle_flic_webhook(self, request):
         """Webhook endpoint for Flic button events."""