How can I start a 'screen' session as non-root user
This is a known problem, if you ssh as root somewhere and then
su to become a normal user:
$ ssh root@server # su -l anthon $ screen Cannot open your terminal '/dev/pts/3' - please check.
It is e.g. described in these posts from 2005
The solution is to directly login as the user you want the
screen session to run as.