Get an net::ERR_EMPTY_RESPONSE when deploying Angular application on production server – Apache

I create an Angular App which works great on my development machine.
Now, I am trying to install it on a Windows production server.
For this I have install apache in order to serve this App and also the Rest Service API that goes with.
If I open a web browser and the server and use my Angular App through public IP (https), it works well.
If I do the same from another machine, I can reach the first login page but when I want to login I get the following error message:
-> OPTIONS http://localhost:5001/users/authenticate net::ERR_EMPTY_RESPONSE

I try to configure the Firewall but that doesn’t help, I read many topic but can’t find any answer.

The rest API is done in C#, the startup Configure function looks like this:

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
        {
            loggerFactory.AddConsole(Configuration.GetSection("Logging"));
            loggerFactory.AddDebug();

            Console.WriteLine("Hello Welcome to WebAPI service");

            // global cors policy
            app.UseCors(x => x
                .AllowAnyOrigin()
                .AllowAnyMethod()
                .AllowAnyHeader()
                //.WithOrigins( "http://localhost:80" )
                //.SetIsOriginAllowed( isOriginAllowed: _ => true )
                .AllowCredentials());

            app.UseAuthentication();

            app.UseMvc();
        }

The call to the API from Angular App looks like this:

return this.http.post<any>(`${this.env.apiUrl}/users/authenticate`, { username, password })
            .pipe(map(user => {
                // login successful if there's a jwt token in the response
                if (user && user.token) {
                    // store user details and jwt token in local storage to keep user logged in between page refreshes
                    localStorage.setItem('currentUser', JSON.stringify(user));
                    this.currentUserSubject.next(user);
                }

                return user;
            }));

The env.js file :

(function (window) {
    window.__env = window.__env || {};

    // API url
    window.__env.apiUrl = 'http://localhost:5001';

    // Whether or not to enable debug mode
    // Setting this to false will disable console output
    //window.__env.enableDebug = true;
  }(this));