There is a reason why you shortlisted this person for an interview, and you would not want to lose them over something out of their control, i.e., a family emergency, traffic, etc. So, this will give you a chance to reschedule the interview (if they’re still interested).
Typically, it is good to send these a few hours after the interview time or you can wait until the end of the day, just to give them enough time to reach out first.
Offer to reschedule
Email subject line: Interview with [Company Name]
Hi [Candidate’s First Name],
Just touching base regarding our scheduled interview today at 3 PM for the [Title] position with [Company Name].
Can you please let me know if you are still interested in the position and would like to reschedule the interview?
I hope to hear from you soon.
Best regards,
[Your Name]
[Your Job Title]
[Company Name]