www Get plus headers dictionary works fine on Android but not on iOS

I know this has been an issue, but there are no answers, especially since hashtables are depricated and we have to use dictionaries.

This is my code to fetch a JSon-String from a server. It works fine on Android, Mac etc, I can fetch the data from a php script, but iOS apparently does something differently, I only get a “400 Bad Request” error from the server.

IEnumerator WaitForRequest() {
  Dictionary<string, string> dict_api = new Dictionary<string, string>();
    
  string url_api = "https://api.quizlet.com/2.0/sets/mysetsid";
  dict_api.Add("Authorization:", "Bearer mycodexyzf19f6611b11aea488d2e6aa08d762");
    
  WWW download = new WWW (url_api, null, dict_api);
    
  yield return download;
}

Is there any reason why this does not work on iOS and is there any possibility to make it work?

We found the error in the end and as it might happen to somebody else: So much time spent on such a tiny problem:

In the key I use “Authorization:” with a colon. This works fine on every platform, except iOS. When I delete the colon and write “Authorization” instead, it works. What a crazy, time consuming error…