I have seen some posts regarding this, but they all use a web adapter and there are no conclusive answers that I can find. We are not using any web adapters because we are using a load balancer and there is no web tier authentication (ESRI approved design).
I install the first site and create the Portal. Add the second site to the existing Portal and it registers fine. I can see both machines in \portaladmin and their status is good. I can login to the first machine in the site, but get a Invalid redirect_uri portal Error: 400 signin error when using the second machine. For example:
https://machineONE.com:7443/arcgis/home/signin.html Original machine created site. Can login.
https://machineTWO.com:7443/arcgis/home/signin.html Added to existing portal successfully. CANNOT login, however I can login to /portaladmin.
Before I set up the load balancer both of these need to work.
Why the redirect error?