If you need new passcodes, there are multiple ways you can request them.
On your phone, go to Duo Mobile. Tap the entry that says "CalNet - UC Berkeley" to generate a passcode. This works anywhere, even in places where you don't have a WiFi connection or can't get cell service.
You can also request passcodes by logging in to the CalNet Account Manager and selecting Get Backup Passcodes at the bottom of the Device Control Panel screen.
You can click Text me new codes at the bottom of the second-step verification login screen.
Then, check your cell phone for a text message with 10 passcodes. You can enter any of these codes for the second-step verification.
Note: Passcodes are single-use only; you must enter a new passcode each time you verify.