Hi Madhu,
Can you try to add Thread.sleep before your driver.findElement statement.
It works in Chrome browser but the same does not work in Firefox. Not sure, why?
driver.findElement(By.xpath("//*[@title='Submit for Approval']")).click();
The webdriver is able to identify the element using the above xpath and clicks the button in Chrome. The same code fails in Firefox. I am using the latest version of webdriver and my firefox version is 44.0.2.
Finally I am able to get it working in firefox. Once the script ran in Chrome successfully then it automatically ran in firefox without any issues. I do not know the exact reason for this behavior, but it worked.