Dear Rov I’m moving into a new building that uses facial recognition to let one enter the building. Guest have to ring bells. What should one do during Shabbos?

As you also figured face identification triggering electrical circuitry is tantamount to pressing a button to connect electricity and prohibited during normal conditions on Shabbos. However, you may wait until someone else enters or exits the building, and then follow. Horav Shlomo Miller’s Shlit’a opinion is that this is permitted even if the one entering or exiting is Jewish.