Please post the output of the below to investigate further:
systemctl status mongod.service
telnet 127.0.0.1 27017
netstat -an | grep LISTEN
systemctl status ufw.service
iptables -L
Please post the output of the below to investigate further:
systemctl status mongod.service
telnet 127.0.0.1 27017
netstat -an | grep LISTEN
systemctl status ufw.service
iptables -L