This error "Could not register, Email has already been taken" occurs when the email address has already been registered with a worker in Acall.
We use worker's e-mail address as a unique key in Acall. Within one company, same email address can not be used in any case, including discharged workers.
How to check an existing email address
Click on [Organization] > [Workers] and search for the email address in the search box in the upper right corner.
If the email address is not registered, check the email address of discharged workers as well.
Click the three dot leader in the upper right corner, turn on [show discharged users], and search for the email address in search box in the upper right corner.
If you want to change the email address of a resigned user, please refer to [Cancel worker resignation].