Marriage to a Cambodian woman: issue with the certificate of custom

Hi everyone, could someone help me out? I can’t find a solution because I need to get married in France with my partner, who is Cambodian. Her birth village refuses to provide a certificate of custom—they just won’t do it. I contacted the Cambodian embassy in France, and they told me that her village’s town hall should just give her a document stating they can’t issue it, signed and stamped. So, my partner went back and asked again in writing, but they still refused. At this point, I don’t know what to do, especially since my partner has to come to France in September to get married at the town hall, and they’re asking for the same thing. Can anyone help? Best regards.