We need to create a vapid public and private key

src/Model/Subscription.php

@@ -19,6 +19,10 @@
  *
  */
 
+ /**
+  * @see https://github.com/web-push-libs/web-push-php
+  * Possibly we should simply use this.
+  */
 namespace Friendica\Model;
 
 use Friendica\Database\DBA;
@@ -104,6 +108,6 @@ class Subscription
 			$keypair = Crypto::newECKeypair();
 			DI::config()->set('system', 'ec_keypair', $keypair);
 		}
-		return $keypair['vapid'];
+		return $keypair['vapid-public'];
 	}
 }