FYI - I figured this out for myself. Turns out it was timing out trying to send emails and the gateway was setup incorrectly - when it tried to moved the order through the system, it also tried to send an email and as it couldnt it timed out instead
Hey all, I have 2 shops - both setup at teh same time, both front ends working well but 1 will not move orders through whilst the other works perfect. I keep getting this error: 504 Gateway Time-out The server didn't respond in time. Any thoughts please?