As noted here :
https://docs.hetzner.com/robot/dedicated-server/firewall/#out-going-tcp-connections
make sure to include a rule in your hetzner Robot firewall / firewall templates if you want to connect to the outerworld. For instance, without the "outgoing" line in my setup, I was not able to perform even a apt-get update.
Hetzner Servers - Robot Firewall / rule for outgoing trafic
- Name : outgoing tcp (for example)
- Source IP : N/A
- Destination IP : N/A
- Source port : N/A
- Destination port : 32768-65535
- Protocol : tcp
- TCP Flags : ack
