If none of the devices can be used as the Main Node, make sure
that:
• One of routers has a public IP, either static public IP or
dynamic public IP.
• Port is open, default is 51830.
• If the router is behind NAT, you may need to set up
port forwading.
You can also change port and try again.
If there are more than one device can be set as the Main Node,
you need to choose one to continue.