5 Matt > root

$ ssh -i id_rsa matt@10.10.10.160
Enter passphrase for key 'id_rsa':
Connection closed by 10.10.10.160 port 22

$ ssh -i id_rsa root@10.10.10.160
Enter passphrase for key 'id_rsa':
root@10.10.10.160's password:

So password is right but not accepting.
Looking at /etc/ssh/sshd_config, we see

redis@Postman:~$ cat /etc/ssh/sshd_config | grep Matt
DenyUsers Matt

redis@Postman:~$ su Matt
Password:
Matt@Postman:/var/lib/redis$ whoami;id
Matt
uid=1000(Matt) gid=1000(Matt) groups=1000(Matt)