As nobody here knows what is wrong with the machine，we must send for an engineer to handle the problem.

中文意思：由于没有人知道这台机器出了什么故障，我们必须派人去请工程师过来除了这个问题.

knows 后的从句 what is wrong with the machine 为什么不用陈述语序？

回答如下：

(1) What is wrong with sth/sb? 某物/某人出现什么问题/故障？

(2) What is the matter with sb/sth?某人/某物怎么啦？

备注：（What 在这里已经是做主语，已经是陈述语序结构啦）

He can tell at a glance what is wrong with the car. 他一眼就能看出汽车有什么毛病。

I can't twig what is wrong with her. 我不明白她怎么了。

Have you figured out what is wrong with your car? 你找出你汽车的毛病了吗?

What is wrong with your kite, Jake? 你的风筝怎么啦？

What is wrong with your convertible? 你这辆敞篷车有什么问题？

That is what is the matter with you. 这是你的问题所在。

What is the matter with you tonight? You are quite out of sorts. 你今晚怎么啦?干吗这样没精打彩的。

We all wonder what is the matter with the new machine. 我们都不知道新机器出了什么故障。

What do you think is the matter with the TV set? 你认为电视机怎么啦?