Universal Link not working

Question

I need to open my app from the email. this is the email url: http://staging.imixedtape.com/accept_invite?token=be484a99b1f4554e42b7232dc2268c5e

And for this i need to integrate universal link in my app. this is my apple-app-site-association file which opens via: http://staging.imixedtape.com/apple-app-site-association

it returns:

{
  "applinks": {
  "apps": [],
  "details": [
    {
      "appID": "ZVDN92A33X.com.lemondeit.mixedtape",
      "paths": ["*"]
    }
  ]
   }
}

Still my app is not opening up from the link provided above. I have added the domain "staging.imixedtape.com" in the associated domain capabilities tab. I don't know what's left. also the apple-app-site-association file is uploded onto the root of the server.

Also i have edited my scheme to Release rather Debug, and i am testing it on the real device