Could be any number of reasons @Techsupport
Try uninstalling the app, rebooting your phone and installing again.
Can you login to the web version, and does that work?
How long has it been since you joined o2?
If not long, give it a couple more days and see if that works.
If longer, and the web works but not the app then get in touch with customer services.
To do that, try calling 202 or 0344 809 0202 (assuming you are on a contract), OR 4445 or 0344 809 222 (PAYG).
Best time to call is 8am.
Or you can message O2 on Facebook ( https://o2uk.co/O2CFB) , Twitter ( https://o2uk.co/O2CTW) or Instagram ( https://o2uk.co/O2CIG), hopefully they should be able to help.
Please note, this is not customer services and we cannot access your account. Do not publish personal details (email, phone number, bank account).
Link to our guide on how to contact them can be found here
