看下这句话有语法错误吗 谢谢

有
I mailed a letter on the refund about two weeks ago,.but I haven’t received the due money up now, may I ask what the case is ?
I mailed a letter on the refund about two weeks ago,.but I haven’t received the due money up now, may I ask how to case?

个人观点
前半句 refund 应是for the refund，最后，没有how the case 的说法，要么“may i ask the case/it”或“may I ask what had happened”

I mailed a letter on the refund about two weeks ago,.but I havent received the due money up now, may I ask what the case is ?

貌似。么有吧