moodle webservice(mod_quiz_save_attempt) is no longer working

I am working on a project where i am using moodle quiz feature. and I am using below mentioned webservice all are working but except (mod_quiz_save_attempt)

mod_quiz_start_attempt // working and getting response correctly

mod_quiz_save_attempt // not working from yesterday , but getting response without any error

. . . etc

Reponse of 'mod_quiz_save_attempt' webservice:

{
"status": true,
"warnings": []
}

But answers are not saving into the database

Any help please.