AMD Engineer Co-Op interview questions

The interview was for the position of Co-op engineer for the Spring semester. I had submitted my resume to University Relations long back and seeing a match for my academic projects with the job requirement, the Hiring Manager called me first and took phone interview. It was a perfect match for my projects and the work that I would have to do at AMD. So he was pretty much convinced and told me an other senior engineer would take me interview. There was time constraints so this happened 2 days later and the senior engineer asked mostly technical questions from C++, Verilog, Computer Architecture, Algorithms and also told me to explain the Academic projects in detail. The interview lasted an hour. I think they were impressed by me, So I got the offer by the next day.

First, I got a call from HR and asked for the my availability. The HR wasn't interested in giving out his email id for further contact. He told me he'll get back to me in order to set-up the interview with the interviewers. After waiting for 3 days without any contact, interviewer from AMD suddenly called me out of no-where and started the interview process by asking questions related to my projects on resume. Had a satisfactory interview with the interviewer who was also hesitant to give his contact details, still managed to take his email id in order to send him a thank you letter/ followup letter. Even after weeks no one called/ notified me about my status despite my weekly follow-up.