not immediate notifications

This plugin will send push notification subscribed tokens to firebase and Firebase is sending push notification. It will be delivered immediately. Please check this plugin demo in site Plugin help demo link. In this link, subscribe to push notification and post some activity you will be notified. I am not sure about your site and delay, there will not be any delay unless there is some server problem

Thank you but i am not getting and notification to accept for push notifications.
Do i have to create account ?

If you access using mobile browser chrome, please make sure notifications option in phone settings for chrome browser is ON

i use laptop and firefox

I have attached image showing invalid firebase application server key for push manager screenshot from your website for your reference
invalid-application-server-key

I found in your website Firebase applicationServerKey is invalid. DOMException: Failed to execute ‘subscribe’ on ‘PushManager’: The provided applicationServerKey is not valid in the console log. Please make sure all firebase credentials are correct
Sign in to Firebase, then open your project, click settings icon & select Project settings
To get Firebase server key (for field 1 in admin firebase settings)
project settings > cloud messaging tab > get server key or add server key button to get server key
To get Firebase config fields (for fields 2 to 8 in admin firebase settings)
If you do not have web app, Create a new web app. After creating a new app, it will show firebase config fields
Project settings > General under your apps section > click on config button to view configuration fields
To get Firebase public key (for field 9 in admin firebase settings)
Open the Cloud Messaging tab of the Firebase console Settings pane and scroll to the Web configuration section
project settings > cloud messaging tab > Under web push certificates > Generate key pair to get public key
In the Web Push certificates tab, click Generate Key Pair. The console displays a notice that the key pair was generated, and displays the public key string and date added
(If you already Generated key pair then no need to generate it again)

In your website, in plugin settings, the field firebase public key is wrong it must be 88 characters long. Please go to your firebase account , In the Web Push certificates tab, click Generate Key Pair. The console displays a notice that the key pair was generated, and displays the public key string. Copy the public key/key pair generated and paste it in firebase public key field then push notification in your site will work properly.