Gears

The 4Matic transmission is a bit complex and there can be numerous reason for not shifting. Have you checked the fluid level? Do you have check engine light on? In most cases it can be that the transmission drive selector module fails resulting in the loss of gear selection capability. Also the valve body conductor plate may need to be replaced. If you haven't do the simple things first, fluid level and codes. I believe there is no transmission fluid dipstick, your vehicle probably has a check valve on the bottom of the transmission, you need to go under the car to see it.