Q: Wh can't I select the collect from store on the 16/09 option when trying to pre order the Apple Watch series2

so I'm trying to pre order the Apple Watch series 2 and when i get to checkout, there are 2 options, shipping (3-5 weeks) or available to collect from store on the 16th... However I can't seem to select the 2nd option. Is this because they are sold out or is it a fault?