The My Forza button has not been activated on the UK site. Change your location to the USA and you should be able to access your photos. As with FM3, at busy times, they can take a couple of hours to show on FM.net.
I'm sure I replied to this thread, where are my posts going?
Anyhow, when you take a pic it'll come up 'save?' so you accept and then it should ask 'upload to storefront?' which you have to say yes to as well. Are you doing that?