Your AXS ID will still generate even if there is no internet connection or wi-fi. All you need to do is make sure you login to your account on the app at least once with a connection (if you have an e-ticket, make sure to login at least once after buying your tickets). After that, you will see a prompt at the top of the screen when the app notices connection issues so you can access your tickets offline.
If, for some reason, you are having additional trouble accessing your ticket at the gate, the folks at the venue’s box office will be able to assist you. It will help if you have your ID, the card used for the purchase, and the purchase confirmation email handy.