PwC Associate Tax interview questions

I got a call from a recruiter. They found my linkedin profile interesting and wanted me to come in for an interview. The interview was really long with 12 different interviewers coming in shifts. The questions were all pretty simple though. I got contacted with an offer a few days later, but they have a ton of stuff you have to do before they let you start. Their estimated start date for me is 90 days after I signed a contract with them.

I submitted my resume through a current employee and heard back fairly quickly that they wanted to conduct a phone interview. All the questions were behavioral in nature (Name a time when...) and fairly easy. About a week later I received an invitation to fly up to Boston for an in-office interview. I was one of about 50 people there to interview that day, although I'm not sure how many of those candidates I was actually competing against. Some people were there for assurance positions, or internship positions. Everyone was really nice and welcoming that I met. My morning consisted of a tour of the office and three individual interviews with various managers. Within a week of this visit I received an email saying that they would not be extending me a job offer. I was a bit perplexed by this since they had taken the time to fly me up and pay for my hotel room. Upon some prodding, the only feedback I could get from an HR rep was that I didn't have the experience they were looking for.