Connection refused: AH00957

I upgraded my functional legacy Indico 2.3.5 to most recent.
Apparently, everything went fine, but connecting it says Service Unavailable.
Looking at the log file, I can see [proxy:error] [pid 542] (111)Connection refused: AH00957: uwsgi: attempt to connect to ( failed.
ps aux | grep -i uwsgi
root 1591 0.0 0.0 6248 636 pts/1 S+ 12:55 0:00 grep -i uwsgi
Did I missed something ?

Did you upgrade im place or install on a new VM (as recommended)? For an in-place upgrade there is no step by step guide, but some general advice here.

Anyway, your error and output indicates that uwsgi is not running. systemctl start indico-uwsgi.service should fix it if you installed everything properly.
Don’t forget to also systemctl enable indico-uwsgi.service so it starts on boot.

Up and running again after both actions. FYI, upgrade im place. Many thanks.