Unable to check out online

Have tried multiple times to check out online. Living in Germany, attempting to ship to military APO address. Going through the process for checkout and after confirming shipping methods, I click on "Continue". After that, instead of it bringing me to a payment method page it takes about 1-2 minutes of loading and then brings me to a page with a white background and at the top it asks for email address, last 6 digits of order number or to sign in to get details and track multiple orders.