Hi Saayan,
If you configure environment settings in bashrc,
you can try to comment the following line at the beginning of the file:
# If not running interactively, don't do anything
#[ -z "$PS1" ] && return
Then you need to cd to $TWISTER_HOME/bin/ first, then execute ./start_twister.sh
I guess it should work after these two steps.
If you still see the same problem, please email me again.
Thank you for using Twister.