In addition to "global" Azure support, FortiGate-VM supports "regional" Azure support, including China, Germany, and U.S. Gov. FortiGate-VM deployment on regional Azure clouds requires dedicated subscription accounts as they are not covered by global Azure and services are run under URL domains unique to the regional Azure cloud.
FortiGate-VM is unavailable on regional Azure cloud marketplaces. Instead, you can deploy FortiGate-VM bring your own license instances having a VHD file ready and instantiating a FortiGate-VM instance using your PowerShell or ARM deployment templates by pointing to the VHD file.
You can download the VHD file from Fortinet Customer Service & Support. Go to Download > VM Image, then select FortiGate as the Product and Azure for the Platform. The file name is FGT_VM64_AZURE-v6-buildXXXX-FORTINET.out.hyperv.zip, where XXXX is the build number.
Once the download completes, unzip the file and locate the fortios.vhd file. Upload the fortios.vhd file to your blob/storage location as your deployment templates require.