Urbackup 2.5.21 authentication failure unknown client

I’m having trouble using urbackup 2.5.21 version, with server The error is 'authentication failure uncknown client ', however the authentication key are correct. I’ve changed to another value, and set on the server and client, but I realized that the error persists.

Someone helps?

My mistake. I have too many servers behind a nat, one for each internet client. I’ve forgot to set the Non-default UrBackup Internet protocol TCP port on the server and on the client.

Everything is working for now.