Why is the URI for updating the caption of an Instagram post not actually working, even though I receive a success message?

I am using Facebook graph API Facebook graph API, to update my Instagram page's post create/ update. the endpoint I am using is like

https://graph.facebook.com/{media_id}?caption={new_caption}&access_token={access_token} 

Neither using insomnia nor using JAVA code do I receive the successful message, and the caption remains unchanged.

    private static CompletableFuture<PostFB> updatePostInstagramMessageAsync(String hostname, PostFB ig, HttpClient client) {     JSONObject jsonPayload = new JSONObject();     if (ig.text != null && !ig.text.isEmpty()) {         jsonPayload.put("caption", ig.text);           jsonPayload.put("comment_enabled", true);           System.out.println("jsonPayload is " + jsonPayload.toString());         String url = "https://graph.facebook.com/v19.0/" + "my postID";         HttpRequest request = HttpRequest.newBuilder()                 .uri(URI.create(url + "?access_token=" + ig.page_access_token))                 .header("Content-Type", "application/json")                 .method("POST", BodyPublishers.ofString(jsonPayload.toString(), StandardCharsets.UTF_8))                 .build();         return client.sendAsync(request, HttpResponse.BodyHandlers.ofString())                 .thenApply(response -> {                     System.out.println("Response for updating post is " + response.body());                     if (response.statusCode() == 200) {                                                       System.out.println("Updated post successfully.");                         } else {                             System.out.println("Failed to update post: " + response.body());                                                     }                     } else {                         System.out.println("Failed to update post. Status code: " + response.statusCode());                                             }                     return ig;                 })                 .exceptionally(ex -> {                     ex.printStackTrace();                                         return ig;                 });     } else {         return CompletableFuture.completedFuture(null);     } } 

Despite receiving a successful response, the caption does not change. I have created the application and assigned the necessary permissions:

• pages_show_list,
• instagram_basic,
• instagram_manage_comments,
• instagram_manage_insights,
• instagram_content_publish,
• instagram_manage_messages,
• pages_read_engagement,
• instagram_manage_events,
• public_profile

I am able to create new posts but I cannot modify them. Why? any help would be appriciated.