This will be due to the roles that your staff members have and what each role has been granted access to.
First of all, go to ‘Administration’ > ‘User Roles’ and check to see which roles have ‘Can Access Performance Management’ turned on. If you need to turn it on for a particular role you can do so by clicking ‘Edit’ (on the far right-hand side of the table).
You will need to put a tick next to ‘Can Access Performance Management’. Click ‘Save’ and then repeat this for every role you wish to edit.
Next, go to the ‘User Accounts’ tab and check what roles have been granted to your staff. You may then need to switch back to the ‘User Roles’ tab to adjust the ‘Can Access Performance Management’ option for other roles.