If you use the same authentication app for multiple accounts, make sure you’re using the 6-digit code specific to your Luno account.
Luno’s systems are calibrated to allow some leniency with authentication codes, but a good rule of thumb would be to attempt entering a new code as soon as it becomes available on your device. If this doesn't work, waiting until the end of the code's validity period is also sometimes handy.
One of the other most common reasons for two-factor authentication not working correctly is that the clock on your mobile phone is inaccurate. This can typically be resolved by following these simple steps:
On Android devices, enable Automatic Date & Time option on the system
Settings > Date & Time > Automatic Date & Time
(you can also try to set the time zone automatically)
On Apple devices, change time and date to Set automatically
Settings > General > Date & Time > Set Automatically
If you’re using the Google Authenticator application, select Settings > Time correction for codes.
This will synchronise your phone and the app. If the problem persists, you can do an automated two-factor authentication reset.
If you have the same number, but can’t log in, you can have your account settings reset.
If you have changed your phone number, you can have your account changed.