FortiGate VM on Hyper-V doesn't set SN under CN or SAN in the Fortinet_Factory Certificate

Greetings!

I've been trying to set up a lab using FMG and FGT trial licence VMs on Hyper-V.

I'm able to run both VMs alright individually, problem is when I try to register the FGT on the FMG.

It appears that none of my FGT VMs are able to get their serial number under the CN or SAN fields on the Fortinet_Factory certificate and that makes FMG refuse connections to those VMs.

I've tried redeploying the VM but that makes it "unlicensable" and its SN shows "FGVM00UNLICENSED". In this state, it refuses any attempts I make of licensing it, be it via login to FortiCloud or via license file upload.

I'm running FMG VM version 7.4.7. I would try a lower version to avoid that issue but all the VM images available for download on FortiCloud currently have the same restriction regarding the fgfm-peercert-withoutsn command.

I'm running Hyper-V because I've had no luck downloading VMWare Workstation Pro from the Broadcom portal.

Any help would be appreciated.