If you contact him again, I think it could still happen and be considered part of your application. My DD just did her interview on February 16, more than a month after the application deadline. I haven't seen a ton of activity on the appointment thread, so to my inexperienced eye it looks like they may be reviewing all RA applicants and then sending out a big batch of appointments all at once.
Apparently the admission counselor sends an email to all of the CG auxiliary in the area and see who responds back. He probably sent the email and then didn't notice when nobody contacted him back. If you recontact him, he may at this point more aggressively pursue an area contact, or he may do a FaceTime interview himself (if they do that).
Seeing as how my DD applied to two other academies as well, I see major differences in the process. The most obvious difference is that no nomination is needed, but it is curious to me that the Coast Guard interview is optional when the interviews for other academies seem to be linchpins. (DD requested one in hopes that it would show she was willing to go the extra mile.) I also think the USCGA would be smart to keep the portal up for student review, as she had to contact her AO to see if her interview had been received (it was). However, I will say that the USCGA has been good at returning communication that she has initiated, and as of Thursday they said they'd be reviewing her application within the next two weeks. Thus, if you add an interview to your packet, it would seem that it would be considered (or reconsidered) even at this seemingly late date.
If I were you, I'd send another email.