created users are not appearing in Users or Login

I just rebuilt a Macbook Air with Mojave and updated it. I then created another account for student use (standar). However, after I created the account, it doesn't appear in the list of users. I thought this was a fluke thing -- perhaps I canceled the creation -- and tried creating the account again. I got a red message saying that the account name was already in use. I rebooted the Mac and was only created with the local admin account. I logged in and went back to System Preferences > Users & Groups. No other account. So I wiped the computer and reinstalled Mojave again (after erasing the disk with Disk Utility) and tried the process again. This time, however, I created another admin account -- same results as described above. Any clue on how to fix this? I'm stumped. I've been a certified Mac Pro since 10.9 and have never encountered this before.