Play CORS not working

I have locally deployed my Play app and accessing my REST API via localhost:9000 from within my browser works perfectly.

However, I get the following error when executing a jQuery script (see below) from file:///C:/Users/XXX/XXX//index.html:

Failed to load resource: the server responded with a status of 403 (Forbidden)

No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access. The response had HTTP status code 403.

I followed the instructions given under https://www.playframework.com/documentation/2.6.x/CorsFilter.

My build.sbt:

libraryDependencies ++= Seq(
  jdbc,
  evolutions,
  guice,
  "com.h2database" % "h2" % "1.4.194",
  javaJpa,
  "org.hibernate" % "hibernate-core" % "5.2.5.Final",
  filters
)

My application.conf:

play.filters.enabled += "play.filters.cors.CORSFilter"   

play.filters.cors {
  # allow all paths
  pathPrefixes = ["/"]
  # allow all origins (You can specify if you want)
  allowedOrigins = null
  allowedHttpMethods = ["GET", "POST", "PUT", "DELETE"]
  # allow all headers
  allowedHttpHeaders = null
 }   

NOTE: I tried both allowedOrigins = null & allowedOrigins = ["*"]

jQuery-script:

$.ajax({

    'url' : 'http://localhost:9000/employee/' + user_id + '/weeklyWorkingHours',
    'type' : 'GET',
    'success' : function(data) {
        console.log('Data: '+ JSON.stringify(data));

    },
    'error' : function(request,error)
    {
        console.log("Error: "+JSON.stringify(request));
    }
});

Here is what Play says:

[warn] p.f.c.CORSFilter - Invalid CORS request;Origin=Some(null);Method=GET;Access-Control-Request-Headers=None

You won't be able to get CORS to work from a local file. The browser sends an origin header value of null to the server, and Play won't respond with an access-control-allow-origin header. For testing, you can set up a local web server, for example with

cd c:\Users\XXX\XXX
python -m SimpleHTTPServer

Then you can load your file as

http://localhost:8000/index.html