@Magda7
A quick search on this community, would have shown you the same topic that has been raised ad infinitum..
This is a customer to customer community, so no one can help with access to your account.
But a few things to try:
Login to https://mymobile.o2.co.uk via the web
Clear your app cache on the device
Uninstall the App, and then reinstall it
- Xperia 1V - o2 and Spusu
- Pixel 8 Pro - o2 and Vodafone UK
