The convertible compartment in trunk is not latching, and thus is not allowing the top to come down.
I'm not very familiar with the convertible system on your Mercedes. Doing some research however, I did find the hinges on the cover tend to be problematic. They have plastic bits that break and obstruct the hinge, preventing the trunk from closing. A qualified technician from YourMechanic will be able to inspect and repair your trunk.
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