Complete my season issues

Hello,

I have purchased the first 15 episodes of the Vampire Diaries Season 5 in standard definition from the iTunes Store, I decided to see how much it was to complete my season and was annoyed to see that the 'complete my season' option was not there all the other series I have partially purchased have the 'complete my season' option and the store does recognise that I have purchased the other episodes as it displays the iCloud download button. It does this on both my iPhone 4S and my iPad Mini. I have seen the option for the season before but I haven't seen it there in months. Can anyone help with this? Thank you.