If your csv file only had one user in it, then the error message is telling you it had nothing to do...
It says...
- 0 users created (because the user was already in the system AND the csv file)
- 0 users updated (which is correct because it says the existing user is up to date - was there anything in the csv to update the existing user?)
- 0 users renamed (and therefore 0 renaming errors)
The "Errors: 1" message is the system telling you that it thought it work to do but couldn't actually do anything.
Were you expecting the user to be created or updated?
If updating, did you set the options correctly in the "Upload Users" settings when you uploaded the csv?