can't create webhook through shopify admin api

[taggjan]

I want to create a webhook which will be trigger when the app will uninstall. I try below method in postman and it's return 406 not accetable. My access token is 100% correct but I don't understand why it's doesn't work and also when I try to get webhook count it return {count: 0}.

What I'm missing ?

Request URL: https://{shop}/admin/api/2021-01/webhooks.json

Method: POST

 headers: {
'Content-Type': 'application/json',
"X-Shopify-Access-Token": accessToken,
"Accept" : "application/json"
},

body

{

    "webhook": {

        "topic": "app/uninstalled",

        "address": "https://www.announcementbar.appilian.com/uninstall",

        "format": "json"

    }  

}