Telnet and Root login

Tutorials Tools
1

Hi
this is the question on the Hack the box Meow section:

What username is able to log into the target over telnet with a blank password?

I used putty to connect the HTB Viewer to see am I be able to connect without password by just entering Root and I saw it is not working

Can anyone let me know why?

2

Not sure you already got this. Since the question is generic about username with blank passwords, think of possible usernames. Remember, this is not windows. So be car(s)e-ful and you will get it.