@Harsh Paliwal​ :

The error message suggests that there might be a conflict with the xtables lock.

One thing you could try is to add the -w option as suggested by the error message. You can add the following command to the beginning of your notebook to attempt to release any held xtables lock:

%sh sudo iptables -w -F

If this does not resolve the issue, you might want to check if there are any running processes that are using xtables lock. You can do this by running the following command in a terminal:

sudo lsof /usr/sbin/xtables-multi

If there are any processes listed, you can try killing them with the following command:

sudo kill -9 <process_id>

If none of the above works, please let me know.