1999 c230k Mercedes Benz won't start one click only has new battery

Hello, have you checked to see if the engine actually turns? Getting a breaker bar and socket and turning the crankshaft manually will verify the engine is not seized. If the battery is known good, fully charged and able to handle a load, and the engine is not seized, then check cabling for connection corrosion, tightening and cleaning as needed.If all that is good, it would be a good idea to check for the amount of amperage draw from the starter motor.