How to solve if I get Xpath not worked?

I am new in workfusion,
I want to ask, I get xpath from inspect element but not worked in workfusion. And show Error message "NoSuchElementException".
This example for xpath : "/html/body/form/table[2]/tbody/tr[9]/td[2]/input"
What should I do, to solve this problem?
Thank you Alesia,
Sometimes it's worked, some time failed. How to solve if I get error after Input Iframe and get error "NoSuchElementException" again?