我提交亲属移民的文件里有国内法院签发的离婚“民事调解书" (Letter of Civil mediation), 落款是某市人民法院和法官的名字(The People's Court of XXX city, Judge: XXX)，有英文翻译和国内公证处的公证。
今天收到信要求补材料，说是这个民事调解书 "the letter of civil mediation of divorce dispute is not sufficient for immigration purpose because it was not issued by the appropriate civil authorities.
Submit a legible copy of the final divorce decree signed by a judge or magistrate that shows proof of filing, or the death certificate issued by the civil authorities, that terminated the prior marriage."
国内在法院的调解下离婚的就是发这个文件啊，也有法官和法院的落款。请问该怎么办？谢谢！
