Hi, on Oracle 11g and later the user password is case sensitive (it was not in version 10g and prior ones).
Make sure you input the password (oracle) in lowercase when you create the new connection. Also make sure you select "default" in the role drop box (sys user has SYSDBA selected but normal users must use default) When you query the users table the password is not shown but that does not mean that they do not have password.
I also try to check login:
-> I use "ora1" as user and "ora1" as password. Similar for other examples
-> Role: default
After that I was able to login. Can you tell if this helps for you - what you think ?