If you cannot see your ticket in The O2 app, no need to panic.
Tickets are often uploaded to the app nearer the time of the event, especially if you have bought through an agency such as Ticketmaster or SEE.
Nearer the event if they are still not there you can try the following steps...
1. Make sure you are using the same email that you bought the tickets with.
2. Please try deleting and re-installing the app, also make sure it is updated to the latest version. This usually solves the majority of issues.
3. Contact your original point of purchase to check that the tickets have been uploaded to the app and that there were no spelling mistakes in the email address.
If you still have issues logging in, don't worry, as long as you have your order confirmation email from the time of booking, just try to log in again closer to the event date. If all else fails, please take Photo ID and your order confirmation to the Box Office for further assistance