The Quest for the Elusive ISO
What to know for Red Hat Enterprise Linux 7 End of Maintenance
Use the exact same portal steps above, but select Version 7.9. It will be available under your subscription.
Final verdict
Don't trust random "RHEL 7.3 ISO download new" links. Go directly to Red Hat. If you don't have a subscription, use the free Developer option or consider CentOS 7 (if still available in archives) or AlmaLinux/Rocky Linux 8/9 for modern alternatives.
Compare the output with the checksum on the Red Hat portal.