Hi @rwadhams, no worries, I'm happy to help.
The app is trying to ask for your SSH Port number so it can log into the Pi to install our Cayenne agent software. This would be 22 on a default Raspbian install. Please note that fresh Raspbian installs disable SSH by default now as a security measure, so you may need to ensure SSH is enabled at all on the Pi. See step 2 in this documentation to for how to do that.
I'm guessing that might be why you ran into trouble here: that SSH was enabled by default in the past, and is disabled by default now.
Let me know if this helps or if you get stuck anywhere else!