Tor doesnt allow to be run in root user if you need to run it under root user than modify the start-tor-browser script which in kali linu is present in
/home/.local/share/torbrowser/tbb/x86_64/tor-browwser_en-US/Browser and comment the lines
#if [ "`id -u`" -eq 0 ]; then
# complain "The Tor Browser Bundle should not be run as root. Exiting."
# exit 1