Sing Orthodontics interview questions

Interviewed in person, went very well was invited back and set up for drug test and background check, which had to be completed before working interview. I return for 2nd working (unpaid) interview that went very well and then the employer "ghosted me", no explanation, passed all of the necessary requirements, terrible communication and employees seemed irritated and not helpful. Too busy talking about personal issues and gossiping about patients/other employees.