Xpath cannot be evaluated or does notresult in a WebElement

Am facing the above titled exception,am using two two x path's

1.//form[string(@id='form1')]/div[2]/table/tbody/tr[2]/th

2.//tr[2]/th

Code:

WebElement ele=driver.findElement(By.xpath("//form[string(@id='form1')]/div[2]/table/tbody/tr[2]/th")); Actions act=new Actions(driver);

    act.moveToElement(ele).click(ele).build().perform();

Am running this code in windows 10 IE 11 where am faing problem,works fine in all windows Firefox and chrome combinations.

As there are very less resources regarding this issue,please kindly help me to sought out this issue.

Thanks in advance.