Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
There is a DAS start authorization problem. It is usually a faulty key or bad All Activity Module. Sometimes the DAS module with immobilizer ring is faulty as well. I would start by trying a spare key, if you don't have one, order a new one from the dealership. If that doesn't work, at least you have a spare now. I would replace the All Activity Module that is attached to bottom of the fuse box under the hood.
Were you able to get any parts replaced on your ML?