I assume you are talking about the job page of the company. You have to make a quicksave before you create the job. Then you load the most recent quicksave in the game which is the quicksave you have saved before. Note that the job is already started so the job does not appear in the company's job list. Just go to the marker(on the map) and find the spot where you load. Also make sure you've got the correct trailer hauled if you set an "ownable trailer" cargo or no trailer if you just created the job with company trailer.