Starting with Kali 2020.1, there is no longer a superuser account and the default user is now a standard, non-privileged user. Until now, users have logged on to the system with the user “root” and the password “toor”. In Kali Linux 2020.1, both the default user and password will be “kali”
kali linux invalid password root toor for version 2020.1
If you would like to use root instead here are the instructions to do so:
Issue command “sudo su”
<Enter the password for kali user account>
Issue command “passwd root”
<Enter new password and retype that password>
At this point you can log-off and re log-in or you can just switch the user and log in as root.
Let me know if this helped you.