Your Orbit Card can be used to enter buildings. If it's not working please follow these steps:
Check if your card is registered in your app. Press "You", then "Access card".
If the card is deactivated please activate it by entering the card number in the Orbit app.
If the card has already been activated in the Orbit app but is not working, you could try to deactivate it, and then activate it again. Then restart the app.