Oh my, I don’t know who wrote that guide, but for sure it wasn’t someone very familiar with Discourse at scale.
The last step tells you can add more backends to the load balancer by using the droplet snapshot feature, but since the guide doesn’t mention using Object Storage for the uploads, doing that will completely break user uploads. Also if you follow that guide, updates will become non-trivial.
My advice to @Martin_Bailey is that you should not follow anything there. It will only result in a broken install, as you have found.
Please follow our official install guide if you want a quick and sane install of Discourse. Going off that path can quickly become a full time work.