If at connecting SSH displays the error “Too many authentication failures”, This means that there are more than three failed authentication attempts. This could be because the SSH client iterates over and offers the server all the SSH keys available to it, thereby exhausting all authentication attempts.
To fix the situation, try adding the argument to the connect command
-o IdentitiesOnly=yeswhich will indicate
ssh use only the credentials specified in the command line or configuration file
ssh -o IdentitiesOnly=yes firstname.lastname@example.org