Replaced my battery now it will not start

Hi LAKJ, my name is Alex amd I will be helping you. Here is a helpful link that might help you: https://www.2carpros.com/articles/car-battery-dead-overnight

LAKJ Welcome to 2CarPros.

So you installed a new battery. The engine started fine. Then you tried to start it later and it did what? Turned the key on and nothing? Turned it on and got dash lights but nothing when trying to start it? It clicks or tries to turn over? All of those would point to a different issue. Does the security indicator come on?

I would start by checking the battery voltage. It sounds like you have a low battery from a large parasitic draw or the connections are not real clean and the current needed to turn it over and start it isn't getting through. Another thing you may want to try is to disconnect the battery, then reconnect and go through the synchronization program. It's possible the memory saver didn't keep all of the settings it should and starting over could cure the problem.
Be sure you have all of the info like the radio code before doing this.

Synchronize windows

The one touch or auto close window functions will be erased.
Press and hold the window switch until the window closes completely.
Once the window reaches the top, continue to hold the button pressed for an additional three seconds.
Lower the window and continue to hold the button pressed for an additional three seconds after the window is fully lowered.
Repeat this procedure for the other windows.

Synchronize sun roof

Press and hold the switch to close the sunroof all the way.
Once closed continue to hold the switch for another three seconds
Press and hold the switch to open the sunroof all the way. Once the sunroof opens fully, continue to hold the sunroof for an another three seconds.

Calibrate steering wheel

Once you complete the battery replacement, start the engine. You will be greeted with a couple of warning messages such as ESP warning light but don’t panic. To reset the ESP warning follow this procedure:

With the engine running
Turn the steering wheel all the way to the left and hold it there for two seconds.
Turn the steering wheel all the way to the right and hold it there for two seconds.
Repeat procedure one more time. Straighten the wheels
Turn off the car and restart it. The ESP warning light should be off

Set time

Follow the instructions in the owners manual to set the time in the clock.

Radio Code

Many models require that you enter a radio code after the battery replacement. This is often printed on the owners manual. If you can’t find the radio code, call your Mercedes-Benz dealer. They can look up the radio code if you provide the VIN.