"Save as" to different page name breaks send function

I'm guessing this will be a quick one. I've installed a formmail function with the "Insert new form" function, and it works fine as the original test page, "indextest.php". However, once the test worked ok, I did a 'save as' and saved it to the public file name in the folder "index.php". When attempting to execute the form on the index.php page, it does nothing and just returns the same page with a blank form. The only thing I changed was saving it as index.php rather than the original name, indextest.php.

Is there something else I need to change in the code manually when I rename a page with the email function?

I've attached both incase you need to see them.