What should I do? When you have appointment to interview, but you cannot.
HR’s responsibility is calling to interviewee to appoint, and then if interviewees has changed their mind or canceled. You should inform HR to get the information to show your good manner and make your credit to not get a blacklist.
Tips : You should inform HR to get the information that you cannot to have interview and disclaim because HR would understand you, and they can appoint other interviewee. Importantly, you wouldn’t on a blacklist either.