How to make a patch call to external API from Lithium?

Jhansi_k,

Looks like your issue is with the CORS.

To enable CORS support, and to make Community API REST calls in FreeMarker endpoints or from external domains, you must contact Support to enable cross-origin resource sharing (CORS).

If you need more information, check this artcile https://developer.khoros.com/khoroscommunitydevdocs/docs/getting-started#section-cross-origin-resource-sharing-cors-