If one peer switches to a less restricted network (e.g., mobile hotspot), that often forces direct tunnel.

Converting this to a (indicated by a green dot) requires opening the path between devices by bypassing firewall or NAT restrictions. Step 1: Whitelist Hamachi in Windows Firewall

: Discusses how private P2P tunnels are established and maintained without central administration, which is the core goal of a "direct tunnel".

The most effective fix is manually setting ports in your router and Hamachi settings.

If you have multiple network adapters (e.g., a WiFi card and a Hamachi Virtual Adapter), Windows might prioritize the wrong one for routing, leading to connection errors.

If you cannot achieve a Direct tunnel, Hamachi is broken for your network topology. Do not waste hours—switch tactics.