@murgero @girish
I think I figured it out: I suspect that I changed root's username soon after install, then forgot about it, or did not realize that I did so. I am not sure what happened with the password either, but what I had wasn't working. So I was able to change the email address associated with the (renamed) root account. Then I had to wait a couple days to get a new password while time4vps's occasionally available support opened port 25. It's set up correctly now.
Now that I mentioned it, I will state for the record that time4vps's support is NOT 24/7 like they so proudly state on their homepage. Their hours are GMT +3:
weekdays: 8:30 till 21:30
weekends: 10:00 till 16:30
So if you are on the West Coast of the US you can get support until 11:30 am on weekdays and until 6:30 am on weekends. š