The most common FTP errors are related to incorrect login details supplied or an issue with the hosting server or the internet service provider. In most cases you will see the Could not connect to server error, but exact errors will vary depending on the issue.
"530 Login authentication failed"
The error shows
that your FTP hostname, username or password are incorrect. Your main
FTP login details are listed in your cPanel > Files > FTP Accounts, then Configure FTP Clients under the FTP Acounts heading.
"530 Sorry, but I can't trust you"
This error indicates that the directory which you are trying to access is no longer present on the server. You should check your FTP accounts from cPanel to see the exact path of your directory or create it if not present.
"EAI_NONAME - Neither nodename nor servname provided, or not known"
The specified server hostname (or IP address) is not correct and the connection could not be established. You should again verify your FTP login details.
"ECONNREFUSED - Connection refused by server"
You can see this error if you are using incorrect FTP port number. The FTP port number that you should use is 21.
"FTP connection timed out"
This most
often happens when your Internet Service Provider is restricting the FTP
port - port 21. Another cause for this issue is if you are not using Passive mode with your FTP client.
Additionally, if you are using your domain as an FTP host to connect to, it might not be resolving properly. You can try to use your account's IP instead. You can find your server IP here.
"Your bandwidth usage is restricted"
This message means that there is a bandwidth restriction for all FTP connections to the server. This restriction prevents FTP transfers from taking a big part of the network bandwidth and slowing down the rest of the connections to the server.