I found the solution- 1. I hadn't verified that I was not collecting VAT-2. even though I was on the trial, I had not actually selected the plan that will kick in after 14 days All working now 

I have the same issue - in the 14 day trial with Shopify Lite - have already deleted the Store and the ePOS option s- just have Button sales channel - when I embed the HTML into my website & publish I get the same checkout issue - infact when I click...