Some clubs using Nettla has set up a connection to manage automated light and access for their facility. The entrance system is often based on a timer 'before' and 'after' your sessions start time, meaning that you can enter 30 minutes before to 30 minutes after (or whatever number the club has decided).
If your code is not working for any reason, please reach out to the club directly and ask what their rules are and mention that you are not able to get in. They will either be able to help you with a manual-opening or check if there is something that is not right regarding the automated connection.