Bad Request

hi
i have a target
in post request of my target there isnt any cookies,its application/json content

all the post are USER,PASS and captcha

but at the test on it,i see “BAD REQUEST” response at the response source

i tested all TLS12,SSL and…,not gonna affect

when i leave user,pass field blank,i see the resp source says “username is blank” but at all when i do everything currect i just see the bad request not the “invalid credential response”

Can you send me the code please?