Thanks for the tip. Took a while to find the Admin Center (a triple-dot menu was in the lower-left corner - wasn't expecting it there, usually it's at the top somewhere!) but when I did, saw that I had only the one, free seat. Asked my Administrator about this and she said the trial period expired two days ago. So I hadn't paid for it after all! Once she got it paid for and gave me the credentials for the new account, everything seemed to be fine.
