Andreas and cjcox have good points. I am dealing with ESXi and vCenter 6.7, but will be upgrading soon.
I guess the most important lesson I leaned is not to assume that you have completed the VMware user setup until you have proved that you can log in. I saw another forum entry where the user went through a long troubleshooting process until he discovered that a password had expired.
So my suggestion for the documentation would be to augement the statement ““You must have defined a user on the ESXi-server…” with the suggestion that you test this by using the credentials to login to the web ui and see that this works before proceeding.