Server authentication failed

On the backup server, I noticed a user with this status … it can be seen that the backup is being done, but what does this status mean?

I think you can get this message in internet mode it use a password in addition to the key file.
you can set one pass per client (need to type the same pass on the client and server).

As i remember if it s a key issue , the message is specifically about a key

dont do anything… but today, the problem is gone