This Article covers how to disconnect the Salesforce Authenticator if a Users has lost their phone, gotten a new phone, or has been locked out from accessing Salesforce Authenticator.
The System Administrator User at your organization will need to disconnect the Salesforce Authenticator on the User settings page, allowing the User to set up the Salesforce Authenticator again, or on a new device.
Navigate to Setup
Go to the Manage Users menu > choose Users
Click on the Username for the person who needs Salesforce Authenticator to be reset.
Then click the Disconnect button next to Salesforce Authenticator:
The next time the User attempts to login, they will need to re-setup the Salesforce Authenticator App.