If your IBKR Mobile app has been uninstalled (intentionally or unintentionally), you can install it again and try to recover the activation following the instructions for Case A in the IBKR Knowledge Base.
The same procedure can be attempted if your phone operating system was updated or if your phone was reset or formatted.
If the app is unable to successfully complete the recovery, you would need to reactivate it manually using one of the procedures below: