Unable submit for Zero Trust Free Plan

Hi folks, I'm hoping someone here can help me - I've recently setup a new Cloudflare account, with which I I'm using a Tunnel from my local network. I've then gone to setup an application, prompting me to get the Zero Trust Free subscription - I provide a payment method, billing address, select the plan, hit the purchase button and nothing happens. I've tried both Firefox and Chrome, attempted different payment methods (CC and PayPal) - CC pre-authorisation comes through on the card statement (so all good there). Also switching Payment Method/Backup Payment method with no luck. Taking a look in the browser dev tools, when submitting the "Purchase" button (image attached), I can see a /subscriptions API method come back with: {“success”:false,“errors”:[{“code”:1000,“message”:“Internal Server Error”}]} I've submitted a community post here - https://community.cloudflare.com/t/unable-to-purchase-zero-trust-free-plan/698827 And also a Billing support case here - https://billing.support.cloudflare.com/support/s/case/500Nv00000CiLxx No responses yet, so any help would be very much appreciated as I really love Cloudflare as a tool for work, and keen to utilise it in my personal stack