I'm receiving a certificate warning when I try and order photos

This only happens on some Apple Macs when using Safari  The issue is
with some corrupt certificates that are being stored in the Keychain Access

The website “[arphotos.com.au]” requires a client certificate.

To fix the problem,

1. Go to Finder > Applications > Utilities >Keychain Access
2. Search for the name of the certificate(s) that showed up in the certificate window above, and delete them all.
3. Then restart Safari and try again.