Hi, I hope you already got the interview.
I made an account just to reply to you in case you haven’t.
I was in the same situation as you. Tried to set an appointment for K1 interview since April or May 2021. I went on the website to check almost everyday (except Sunday). And there was nothing. Finally on May 22 2022, somehow there was one slot open (yes, only one slot) on June 16. So I had an interview like 2 weeks ago.
Hope u already got the interview. If not, keep checking everyday. I know how desperate it feels, but keep going on. Good luck!!!!