Won't calculate delivery and can't check out

Highly annoying. Won't calculate delivery, giving error message, and then stuck without being able to proceed to check-out.

Been doing this all of May, had to place multiple orders, and pay shipping charges as the only time it'll work is super early in the morning, and I'd just go for it when it worked.

Now stuck again, and I just can't get passed it.

And there is no customer service to call, and they don't reply to emails. Are they even aware of the issu?