Hi paulak1,
Are they opening the payslip from the email link "Download your pay slip now"? If they're getting blocked from opening the payslip after clicking this link, it's possible that their device might have heightened security measures, such as a firewall or anti-virus blocking the attachment. I would recommend that they try opening the payslip from another device, such as their phone, and see if the error persists.
It could also be their email provider warning them that the attachment is not secure. They may have to configure their email settings to allow the opening of links in emails.
Bonny