If Deltamatic does not have a confirmed MCO-MIA segment, you will not be able to check-in. If your e-ticket exisits in the PNR but there is no corresponding segment, you will most likely be put on the stanby list. I world call DL and ask them to check the PNR history to see what has happened. Then you may need to fight with LA and/or Travel Agency to have the segment reinstated. Good luck.