Did you run the full install script over the top of a re-existing install?
When you say 'old users' it makes me think that may be the case. Can you confirm first if you ran the update script as well as which version you attempted to do this from.
That error implies there is just no connection to rTorrent. It's possible if you are coming from a version in the 2.3.x range you may need to remove cron from your system to take advantage of systemd, which is now our standard. Another possible cause is that running the full install script on top of an existing install attempted to re-add a new port range for scgi-localhost... this hasn't been the case in beta tests, but it's a very small possibility.
The only other explanation is that something was manually adjusted by you and it threw everything off kilter. To this you would need to trace exactly to when the issue occurred.