With the two-factor authentication enabled, there may be a situation when your smartphone doesn’t have battery to answer the code challenge, or the device has been lost, etc.
Fortunately, in cases like this you can use the One-time codes functionality to gain access to your account securely. This function allow you to generate and save multiple backup codes to use in case of emergency. The total number of one-time codes can be configured by your domain administrator.
In order to see the codes go to Preferences > Accounts > Account Security and click on the View option next to One-time Codes. Here you will also see more options like Trusted devices and Applications (if your domain administrator enabled these functions).
The unique codes will be displayed in your browser / on your device and you can then save them and store them securely (written somewhere, in another device, etc.).