A user's email serves as a unique identifier in Upfront and can only be used once.
Adding a user to a location
If you are trying to add a user to a new location, rather than trying to add a new user, you can assign them to that location within user management.
What if I don't see the user in my account?
In this case, one of two possibilities exist:
The user is set up in your account, but under a different location
When the user is in your account, but in a different location, you simply need to contact your account owner or an account admin to have them add this user to your location. Directors and managers who have access to both the first location where the user currently is assigned and the secondary location to which you would like the user assigned, can also perform this action.
The user is set up in a different account
Currently, if a user email address is set up in a different business account, you will not be able to use that email address in your account. The best solution would be to set up the user with a different email address.