REST API The requested resource does not support http method 'OPTIONS'

I am trying to make a REST API call using AJAX to IMIS using bearer token (which is retrieved using C#) from another site. In other words I am making REST API call to IMIS scheduler endpoint from a different domain.

I know I need to handle the CORS issue so I put in the statements like

....
and stuff like that.

But I am still getting 405 ERROR from the response saying "The requested resource does not support http method 'OPTIONS'".

Does anyone get the same issue and have that resolved successfully ?