Did you put in the ROOT password first? Dev commands are also case-sensitive, so make sure you type them exactly as they're presented in the terminal!
There are just a couple things I can think of that might be the issue!
1. If you closed the terminal after putting in the password the first time, and then re-opened it, the password will need to be re-entered again
2. Item IDs might not be input correctly, make sure to do "/ls" after the force command to get the correct IDs