WordPress Redirection not working on live website

Hi Guys,
My WordPress website is now live unfortunately the ‘Redirection’ Plugin I use to manage 301 redirects is not working on the live website but is on the testing website.

Here is an example of the same redirect working and not working:

Testing website:
http://agl.adelantedesign.co.uk/How-to-Install-Artificial-Grass.php  Redirects successfully to: http://agl.adelantedesign.co.uk/how-to-install-artificial-grass/

Live website:
http://www.artificial-grass.com/How-to-Install-Artificial-Grass.php  Does not redirect.

Is there anything you can suggest to fix or diagnose what is causing this?

Really hope you can help.

Thanks,
Richard