Please am having this issue ,2009 benz s class 4matic smart key wont turn in ignition

normally once the smart key enters the ignition the screen with the benz logo comes on but now the key wont turn to start the engine and also the lights are not coming on

Replace the battery. If that does not work. Run a scan on the car to diagnose the possible error.

Did you drop the key recently? those keys have chips inside them that communicate with the vehicle's immobilizer if the key or chip is damaged its not going to work. If you have a spare try using it

@maninmood, will replace the battery with another and see if it works ,will get back to let you know how it goes
@leuelliot the key did not drop ,will try the spare
thanks guys appreciate your support will get back to let you know what comes up thanks once again