I had a very similar error. For me it was because the environment variable FTP_PASSIVE was not set to 1, causing it to not connect passively.

I could see the errors better when I connected via
 my $ftp= Net::FTP->new("server", Debug => 1)
and in the debug I saw

Net::FTP=GLOB(0x86cb364)>>> PORT 192,168,201,177,249,218
Net::FTP=GLOB(0x86cb364)<<< 200 PORT command successful. Consider using PASV.
Net::FTP=GLOB(0x86cb364)>>> ALLO 22246
Net::FTP=GLOB(0x86cb364)<<< 550 Permission denied.