MB USA Does not have the best I.T. techs working. Even with our Mercedes-Benz customers, it is a hit or miss affair. And they keep having issues with it still, they have to pull it down for a week at a time :-(
But, I can help... Call this #: 888.628.7232 (Mercedes Me Help Line). I speak with Tasheena when I call.
But, it does have to be initiated at a Mercedes dealer. FYI it only works with 2019 & 2020 models for MB, I am sure it is the same with Smart. Have the 2019 Smarts even hit the streets yet?
A quick call to these guys, will at least get you to a final conclusion!
If they say its possible with your car, I can probably complete the process for you here...