H4 visa status says 'Refused' since April 2023

My sister applied for H4 visa renewal through dropbox back in April 2023. She picked up the passport and later realized there is no H4 visa stamp. Upon checking the CEAC website, the status says ‘Refused’. There is no communication from embassy on why it is refused and what additional docs they need to approve the case.

Can anyone advice on what is our next step? how can we contact embassy?

Along with passport , she might have received the slip asking for more evidence and deadline date for it. Did she checked it properly?