King of teh Monsters

After my minecraft name has been changed, I couldn't login on the technic launcher, please fix this. My former minecraft user name was hyvesisdood. That user name has been changed to King_of_Monsters. Password hadn't been changed. After this, I tried to login with the right user name and pass word, but I got then this auth error: Invalid credentials. Invalid username or password. How can I fix this?