1. Verify whether the client has been started and whether the connection between server and client is OK. 2. Verify whether Simple File Sharing has been enabled on the client; if yes, disable this feature. 3. Verify whether the username and password are correct. 4. Verify whether firewall has been enabled on the client, including Windows firewall; if yes, disable the firewall temporarily until successful monitoring, or you may add the program to “Exceptions”.