A few weeks ago I had some problems installing Engagement Centre on my employers internal Connections 5.5 servers. I installed it as I did with a 6.0 Connections server but each time I went to https://connections.acme.com/xcc/main I was redirected with a 302 to https://connections.acme.com/xcc/admin#ContextRoots?redirectUrl=/xcc/main which is the context roots page.
I checked the context roots were correct and they were. I went back to the customization screen and ensured I had saved it.
It still wouldn’t let me go to /xcc/main to start creating pages. I logged a PMR and Charlie Price got involved and reproduced it. It was an embarrassingly easy fix. I needed to go into the context roots screen and click save even though the values were correct and didn’t need changing. After clicking save I could go to /xcc/main and create my pages. Simples.