This usually happens when two-factor authentication (2FA) is enabled for the CORE user. When 2FA is active, CORE restricts certain user management actions, which can prevent updating the user’s email address or deleting the account.
To resolve this, reset the user’s 2FA settings, then delete the existing user account with the incorrect email address. Next, create a new user for the existing employee using the correct email address. The user must accept the new invitation email and complete the activation steps again.