What could be the reason your ship date being pushed back?

Medical. Administration. Lack of Class Seat/Date. Any number of reasons. Have you spoken with your Recruiter as to why your Ship Date was pushed back?

Several reasons. It could be anything from medical hold, other administrative issues holding up the works, funding, transportation, there could be delays due to weather/natural disaster/safety concerns, lack of seats, and the list goes on. Talk to your recruiter.

Any number of reasons...no one on here is going to know why yours was for sure.