CDR FTP push issue

Hi I have a 3820 Acme Packet SBC ECZ730m2p18 version

I configured account-config -> push reciever for push CDR via ftp

    push-receiver

        server                 10.1.2.3

        port                  21

        admin-state               enabled

        remote-path               /AP01

        filename-prefix

        priority                0

        protocol                ftp

        username                CDRFtp

        password                **

Everything works well in this configuration. But if I change the port to something other than 21 (1121 for example)

the service stops sending CDR files. Of course, I change the port on sbc and on the FTP server.

I see message on acmelog

radd@ACMESYSTEM-2: MINOR CdrPushRecvManager::FindRecvrHunt skipping! Receiver 10.1.2.3 is not eligible for service.

What is the reason? how to change port for FTP?