Remove the front grill, the passenger side turn signal, then with a light look up to the firewall high and to the right.
there is a U shaped black rubber hose that can be pulled off. It often has debris in it that prevents water flow.
Cut the end off. Mercedes pinched the end to prevent spider ingress.
Don't run your AC till you do this because the water backing up into the car can damage the Canadian E box causing major issues.