Cannot Purchase Kaspersky Standard subscription on the Kaspersky Website

[denacre]

I select 'Kaspersky Standard' > 10 Devices, 1 Year (£23.99) > Buy

(1) Enter your billing information

I enter my details but it tells me my postcode is incorrect, which it is not. I click on 'Proceed to Next Step', but nothing happens.

On the rare occasion I am able to get past that error, I get to:

(3) Add Payment Details

But when I click on OK, nothing happens.

I even tried doing it with a clean profile with no changes or add-ons applied, but I get the same errors.

Really frustrated with this. I used to buy from Amazon, but not seeing it there anymore.