You’re supposed to match the “no” at the end. If you don’t do that then the challenge tests will fail.
The regexp test function returns true or false if a pattern appears in a string. /Oh{3,6} n/ is a pattern that appears in the string, so that function returns true, but it isn’t what you’re asked to do – /O/ will also return true. As will /Oh{3,6}/ or /h{3,6}/ or /n/, but they aren’t the right answers for that challenge.