Problem of connection to the ftp server

[Firefox78]

Hello everybody,
I just installed an F210 and everything is fine in the local network, included ftp server which I can access with FileZilla without any problem.
But I want this ftp server to be accessible from the outside. I set my router to make outside connections possible but, if I can connect from the outside, I can't access to the connection directory, whatever the login account I use.
Do you have an idea of what is going on, what I did wrong? And, perhaps, do you have some trails?
Thank you.
FF78

[TMSupport]

As for remote access TNAS with FTP service, you should forward the port 21 (as defaulted) on your Router and also you can define the Passive port within the range 55536-56559 and forward all the ports on your Router too. For example, you can set the Passive FTP port as 55536-55537, and then you should forward the port 55536 and 55537 on the Router. Here is a link about port forwarding : https://www.howtogeek.com/66214/how-to- ... ur-router/ for your reference.