If you have a staff member in at your school who already has a login to Safeguard Record Manager at another school, you can't just give them access to your school's information. You need to create a separate email account at your school to be able to add them to your Safeguard Record Manager.
Example
Sally Smith already has a login at her school with an email of sally.smith@school-1.com.
Sally is the temporary acting head at school 2. You can't add Sally with her 'school 1' email. You need to create a new email account for Sally, for example, sally.smith@school-2.com and use that to add her to Safeguard Record Manager.