You and lots of others
Can you use https://accounts.o2.co.uk/signin?
If so delete the App, reboot the phone and reinstall
Otherwise
You will need to contact O2.
Message them on Social Media. Facebook (https://o2uk.co/O2CFB) , Twitter (https://o2uk.co/O2CTW) or Instagram (https://o2uk.co/O2CIG)
Or phone them on 202 or 0344 809 0202 (contract)
4445 or 0344 8090222 (PAYG)
This is not O2 and we are all customers here similar to yourself and cannot answer account type queries.
