Fair HQ sends a maximum of 3 reminders every 3 days to employees who haven't completed their survey yet.
To send another survey link at any time you can either:
tick the recipients in Audit > Employees then choose the
all selected (#)button at the top of the pageor use the
all incompletebutton to automagically remind everyone who hasn't completed it yet.
If they've never been sent an invite (i.e. they were added after the original sending), the system knows. They will get a fresh invitation and will be signed up for the usual reminders. Anyone else just gets a one-off reminder.