The windshield washer is not working even though the reservoir has water. I can't hear the pump working.
The symptoms you describe lead me to believe you have either a washer pump motor that has failed or the connection to the washer pump motor has a break in it. To be 100% certain it may be time to enlist the assistance of a certified mechanic to examine exactly what may be going on here in person. They will be able to diagnose your car’s wiper fluid issue and determine if you have a bad fuse, bad wiring to the washer pump, or if your Mercedes needs to have its washer pump replaced.