Advotics Senior Software Engineer interview questions

I applied online through linkedin, the process took almost 2 months. I passed all stages (5 stages) including background check. The recruiter said an offer was being made. then I was ghosted out for almost 2 weeks. with no reply at all. then i got a HR lead email from one of their employees on linkedin. after I emailed, I got an automatic rejection email. I do not know why. a total waste of time. so dissapointed. if I didn't try to find out, maybe I would never have been notified. so unprofessional