Ftp in active mode , backup

We have changed our ftp server to accept connection in Active mode and ever since pbx gets ftp connection error while we want to save backup on the ftp server.
and ftp from ssh connection gives me 421 connection error.
There is no firewall set and I see Syc/Syn-Ack/Ackj sequence in pcap, however , I get RST from ftp server when ftp client ( pbx ) is sending Syn from a port more than 45000 to ftpserver:21.
Since we have different pbxs, I can see if pbx is sending request to port 21 from any port under 45000, we get access to the ftp server, but if ports are more than 45000 , we get RST from tfp server.

Since we can not change our ftp server, any idea how to change ports in our pbx? for our ftp client?

Example Reply
421 Service not available, closing control connection.

A 421 reply code indicates that while the service is still running, the service is unavailable at the time of connection. It usually indicates that the server will be restarting as soon as it finishes processing of pending operations (usually any file transfers currently in progress). It is considered a transient negative response, which means the client is encouraged to issue the same command again at a later time when it may be accepted.

Possible Commands
A 421 reply code may be given in response to any FTP command or connection attempt if the FTP server knows it must shut down.

Thanks for your reply, but ftp server is running since I can have ftp access from another pbx to the same server at the same time. and from web too

do you see anything in the FTP log why it does’t like it?

It was a routing issue and has been fixed, thanks for your reply