Update Projects Task Custom_Fields doesn´t work

Update Projects Task Custom_Fields doesn´t work

Hi, why this doesn´t work? Thank you!

deskmap = Map();
deskmap.put("UDF_CHAR3",desk_weburl);
deskmap.put("UDF_CHAR2",desk_taskid);
response = zoho.projects.update(org_id,projectid,"tasks",taskid,deskmap,"desk_task");