Diligence Soft — items added to cart can't proceed to checkout

I have an order in my cart of nokia 6.
And every time i tried proceed to check out.
It's not going through.
I[censored] can't allow users to purchase the item, then why showed the options to add to cart.

I have added couple of pictures, kindly review it and give me the explanation..

Otherwise i'll take this matter further..