The change password is bugged it seems.
Usually when you get an error message it means your new password is invalid, or it actually changed but gave the wrong error.
When you log out and log back in you can try the new password and see if that works, if not just log in with your old password.
If it won’t let you change you can use the lost password functionality.
To do that make sure you have a email set where you can receive email. (if you don’t you can change it in the account popup).
Then log out, and click the lost password button.
Enter your email there and you should receive an email with a button.
After you click on the button you go back to Curve Fever and you can enter a new password.
We’re remaking the account system currently but it’s not ready yet so it’s kinda a hassle currently