dhcp fails in LinuxMint VM in proxmox in Virtualbox on Ubuntu 22.04

[pve2]

My physical hardware is an Ubuntu laptop and the nesting is as follows :

• Linux Mint: "Linux Mint 21.3"
• proxmox: installed from proxmox-ve_8.1-1.iso
• VirtualBox: Version 7.0.16 r162802
• Ubuntu: "22.04.4 LTS (Jammy Jellyfish)"

For the most part things work well but when I boot the Mint VM, it doesn't automatically get an ip address. If I then set the Mint network interface ip4 settings to "Manual" and add an explicit ip address, then I can connect to the internet from the Mint VM. I believe that, at some level, dhcp is working because the proxmox machine (running under VirtualBox) does automatically get a ip address.

I have already enabled nesting on my laptop and for the virtual CPU that proxmox is running under The proxmox machine has a single "NAT" network adapter with Promiscuous Mode set to "Allow All"

The reason I want to get dhcp working is to test an automatic configuration tool that expects functioning dhcp at the proxmox VM level.

Does anyone have any thoughts on what might be going wrong here?

Thanks.