Can not reach Proxmox machines from Windows host

[Silversub]

Current setup:

• Windows Host Machine A
• Proxmox Machine B (Installed on Virtualbox on Machine A)
• Ubuntu Machine C (Installed on Proxmox Machine B)

Virtualbox is configured using host only adapter. Right now I can:

• SSH and ping Proxmox (B) from Windows (A).
• SSH and ping Ubuntu (C) from Proxmox (B).

However, I cannot SSH or ping Ubuntu (C) from the Windows host (A). The Ubuntu box is receiving an IP through the DHCP Virtualbox host-only adapter so I figured it would be routable from my Windows host. There is no firewall currently on Proxmox or Ubuntu. My Windows host firewall allows SSH.

Is there anyway to reach Ubuntu (C) from my Windows host (A)? Or anything I may be forgetting to address?