It would seem that this part of the update was not succesful
and given the old symlink is still there, this bit must of failed too
which in turn raises questions about where exactly this fell over and what has or hasn’t been updated, and also why there was no indication of an issue.
If it is just the symlink then you should be able to get back up and running by just adding the link manually and restarting the service
sudo ln -sf /home/pi/emonhub/src /usr/local/bin/emonhub
sudo systemctl start emonhub