There is so many posts online regarding CORS, but I can’t seem to figure out what I am doing right, or wrong in order to get this thing to work. My dev team controls our api server and for the sake of getting this to work, we’ve allowed access to all requests coming in, but I am still met with the frustrating error
Access to XMLHttpRequest at 'https://app.mydomain.com/api/login_check' from origin 'http://localhost:8100' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: It does not have HTTP ok status.
When I run my app in a Chrome browser that has disabled-web-security or through a proxy like https://cors-anywhere.herokuapp.com/ it works great, but when I run in a simulator or Test Flight from Apple I am getting the error. I have been working on this for much longer than I ever imagined–please, someone shine some light 
Here is my code:
...
login(username: string, password: string) {
const httpHeaders = new HttpHeaders({
'Content-Type': 'application/json'
});
const options = {
headers: httpHeaders
};
console.log(options);
return this.httpClient
.post<AuthResponseData>(
`${this.AUTH_SERVER_ADDRESS}/login_check`, {username: username, password: password}, options).pipe(
tap(this.setUserData.bind(this))
);
}
...