Jira Rest Client - RestClientException: "customfield=Specify a valid 'id' or 'name' for CustomFieldName"

First of all, excuse my english. It is not my native language.
I am trying to update a custom field, but everytime i testing it i get same error: “customfield=Specify a valid ‘id’ or ‘name’ for XXXXXX”. I have been looking for a possible solution but i found nothing. My code looks like this:

public Issue updateIssue(String keyOrId,List<Pair<String,Object>> customArgs){

        IssueRestClient issueClient = this.restClient.getIssueClient();
        Map<String, FieldInput>fieldMap = new HashMap<>();
        String id;
        IssueInputBuilder builder = new IssueInputBuilder();
        if (customArgs!=null){
            for(Pair<String,Object> arg :customArgs ){
                id = arg.left();
                        builder.setFieldInput(new FieldInput(id, arg.right()));
                        fieldMap.put(id, new FieldInput(id, arg.right()));
                    LOGGER.info("Attribute '"+arg.left()+"' does not exist ");

        IssueInput issueInput= builder.build();
        IssueInput issueUpdated = new IssueInput(fieldMap,null);
        try {
            Promise<Void> result = issueClient.updateIssue(keyOrId, issueUpdated);
            Void vacio = result.claim();
**//Here is where i get the exception**
            LOGGER.info("Issue updated");
        }catch (Exception e){
        return getIssue(keyOrId);

As you can see, i tried with IssueInputBuilder and creating directly an IssueInput. I got same error. I thought that maybe is a value problem but i got issue debugging and saw what was a valid value. I wrote it correctly. SO i have no idea about what i am doing wrong or maybe is an API problem. I have something similar in python and works perfectly, but i need implement this in Java.

Ty so much!!!