I just checked your account- it seems you paid the £7 but haven't yet used your token, so you haven't listed the item basically.
Maybe you started listing it then paid for the token afterwards, but as it shows in the text above the price box, you need to have an active sub or a paid token before you can submit the post.
So - in short, go and list it now! You've paid already so you'll see above the 'price' box on the form it'll say 'Sales Remaining = 1'
Any problems let me know!
Cheers
Chris