Hi Carlos,
If your HANA revision is >= 70 then every time you open the HANA studio and refresh the HANA instance, it will ask the password. But if your using the same user and you dropped the user before to delete the schema of same name then it will not work as the user does not exist.
I see that you want to drop the schema name and landed in dropping user to do that.
If you want to user this user then one option is to re-create the same user again.
Regards
Raj