Sorry for late reply but I had same problem with my Dec 2015 B220 4matic with Garmin Map pilot. it came with a 3 year subscription to TomTom live traffic which worked fantastically well ( auto re-routing etc). When it expired a few weeks ago I could not find anyone in dealership who could tell me how to renew. After raising a complaint with MB customer service problem easily resolved, Just bought a new sd update card (Garmin Map pilot 2018-2019) and inserted . After usual set up have now got new maps and a new 3 year TomTom subscription. Cost £99 and worth it)
Did you buy the SD card from the main dealer? they normally want silly money.