CORS Blocking Issue

Hello All,
Seeking some help as I have been really struggling to get through this error for quite some time now. Here is the issue.

I have my front-end WordPress site that has a menu item called Partner Login.
When the user clicks on the menu item it invokes a function called LoginMember() that is trying to pull up a login form which is tied to my back-end admin server (MVC application) on a different environment. The front-end has a URL of wwww.myserver.com and the backend has a URL of admin.myserver.com. Both environments are in Azure and the CORS policy is set properly. In the browser I continue to get the error message below and am running out of ideas on how to get passed this issue. I have read a number of different postings but still have not been successful getting through this issue.

Access to XMLHttpRequest at ‘https://admin.myserver.com/AccountManagement/PopUpAuth?undefined’ from origin ‘https://www.myserver.com’ has been blocked by CORS policy: No ‘Access-Control-Allow-Origin’ header is present on the requested resource.

Any ideas/suggestions you have is greatly appreciated.

Thank you!