This is the only site i have in una for now.

it was another  site, test one, auto-updated to RC6. now it's deleted, with its cron and DB as well. but still can't upgrade.

On my site update log says :

--------- 2017-12-26T12:03:14+00:00
9.0.0.RC3-9.0.0.RC4 upgrade will be applied
Files permissions are ok and can be overwritten
Files copying successfully completed
Deprecated files were successfully deleted or there is no files to delete
System files hash was successfully updated
System SQL script was successfully executed
The following languages will be affected for system:
- No languages will be affected
System after update custom script was successfully executed