I recently moved into a building signed a 12 months lease in the US. The apartment building has key fobs for entry into the building. There isn’t anyone manning the building main entrance and so to enter I must use the fob. Is there any way to do this with Shabbat observance?

ב"ה Shalom, This question involves full understanding of the electronic circuits involved and what takes place when this key fob is placed. Since, I have very little understanding in this field, I suggest you refer your question to the Zomet institute, whose expertise is in all the electronic gadgetry and Shabbat. https://www.zomet.org.il/eng/ They may also have a suggestion to circumvent the electronic issue. To my understanding, there would be at least a Rabbinic violation of Shabbat to use the key fob. Therefore, you must find a solution. All the best