The FortiGate VM and the Windows Server VM are in different subnets but within the same Production virtual network, which means they can communicate by default unless restricted. Azure allows ICMP between subnets, but Windows VMs have ICMP blocked by default in their firewall settings. Therefore, the likely reason for the ping failure is that the Windows Server's firewall is blocking ICMP (ping) traffic.

Two virtual NICs - The FortiGate Azure Marketplace template deploys the VM with at least two network interfaces: one for the external/public interface and one for the internal/private interface.
One NSG for each interface - The deployment creates separate Network Security Groups (NSGs) attached to each NIC to control inbound and outbound traffic as per Fortinet's best practices.