I can't track my lost/stolen iPhone due to two factor authentication

Log-in to iCloud using https://icloud.com/find

Appending the “/find” allows you to find your phone — and “Mark as Lost” — w/o needing a 2FA verification code.

= = = = =

Going-forward, you should add additional Trusted Numbers to your AppleID to avoid getting locked-out of your account.

This is especially important if you only have a single Apple device.

See detail here:

Two-factor authentication for Apple ID - Apple Support

These are the steps you can perform in such a situation:--> If your iPhone, iPad, or iPod touch is lost or stolen,

and/or:--> Use the Find My app to locate a missing device or item,

and/or:--> If Find My is offline or not working

and/or:--> If Find My iPhone or Find My iPad isn't enabled on your missing device

Regards and best of luck.

Giulio