User in SSH Group

RouterOS Beginner Basics
1

Hallo, I use Mikrotik RB951Ui-2nD (ver 6.48.2) and my new user “SSHUSER” is in group “SSH” (ssh only).
Login as SSHUSER to Mikrotik is correct, but there is error by new ssh connection to my next server: SSH error. no enough permissions

My command:

[SSHUSER@MikroTik] system ssh my-next-server-address user=my-server-user
 SSH error. 
 no enough permissions

What is bad in my user group settings?
Thanks JR.