Why 421 Too many connections
These steps should help fix or avoid the 421 Too many connections error.
What is / causes an idle ftp connection?
Idle ftp connections are caused when an FTP client opens multiple connections, without closing the previous ones, or due to an incorrect setting.
VPS, Dedicated, and Managed hosting plans have the ability to modify the number of simultaneous connections allowed in their WHM; the default setting is usually 8 or 16. Increasing this limit will prevent the error messages that we will review later in this tutorial. Our Shared and Reseller plans allow up to 8 simultaneous FTP connections from 1 IP address at a time, but cannot raise this limit.
Response: 421 Too many connections (8) from this IP
error shows :
Response: 421 Too many connections (8) from this IP Error: Could not connect to server
Now close your file zilla and open it again now
press ctrl+s and window comes before you there just click one at your site manager in left pane. And on your right side of window comes required settings for particular ftp settings and go to transfer settings tab and limit the number to ‘2’.