If the contractor does not start a project on schedule and has not contacted you to notify you in advance, you should call the contractor and get an explanation and find out why you were not notified.

If there is no compelling reason to overlook the failure, you have the choice of either firing the contractor or negotiating a change in the contract to compensate you for the lateness and the failure to provide notice. This might take the form of a modification of the contract to state that despite starting late, the contractor will provide the promised quality of work at no additional charge to you and still meet the sechedule completion date. It could take the form of a revision of the start and end dates, with some type of discount or compensation to you for breach of contract.

You could also resolve the problem by firing the contractor and hiring someone else.