This could be a port / firewall issue.
Ensure the correct port is being used to connect. You will find this in the params file. Remember its not the same port used for connecting your multichaind node.
Ensure multichaind.exe is in your firewall allowed list / or the port.
Ensure your multichain.conf contains
google MyIp and place your public IP if you wish an outside node from your local network to access. if you have a static IP, add the static IP. add you local 192.x address for your local network.