First General Services interview questions

First they had initial conversation over the phone and after one week they called up for the interview over the teams. After that they called for office visit and next day they offered a written offer letter. After next week they realized that I am not of same race as they are and called up for re-interview with third party and they scheduled a re-interview with their IT service provider and once interview was done and they called me over the phone that we are not considering you even you already got the offer letter and all the security checks done.