When changing to a new mobile device where 2FA is enabled for your account, it is usually necessary to first verify your new device within the Authentication app or temporarily disable 2FA. For example, for Google's Authentication app, you'll need to verify your new device as explained here.
To temporarily disable 2FA in Castor, navigate to your Account Settings. Set 'Enable 2FA' to No and click 'Save changes'. Once you have your new device, enable 2FA again for your account. A new QR code will be generated, which can be used for your new phone.
If you cannot access your account anymore, e.g. because you have lost your old device, the Castor Support team can manually disable the 2FA for your account. To request this, please submit a picture of yourself holding your ID to firstname.lastname@example.org. To avoid delays, please ensure that sensitive data such as social security numbers are obscured, as we are unable to process images containing sensitive personal information.
After we have disabled 2FA for you, you can enable it again using the new device.