I have tried to load a layer from a Web Map Service and it did not work. After a few attempts, I used the CORS filter and it stopped indicating “404 Not Found”. Now the error is, “Resource interpreted as Image but transferred with MIME type application/vnd.ogc.se_xml”.

Could someone please assist?

That particular MIME type from a WMS server indicates an exception occurred on the server. Take a look at the response the server is returning using your browser’s network debugging tools. There should be more information about what went wrong in the response.