Command 'rvm' not found, but there are 19 similar ones.
Open your terminal.
At the top menu bar, click on Edit, navigate to Profile Preferences and select the Command tap.
It shoul open a window as shown here in this picture
Select Run command as login shell
Select ok and close.
Close every opened instance of the terminal and restart.
This should fix it. I will be happy to get your feedback if it works for you.