So, following jhoops summary above:
You can connect to the VPN.
You can connect to the Zyxel managed switch inside your network with a 192.168.x.x address.
You can connect to a non-POE device (printer) with the same 192.168.x.x subnet addressing on that same switch.
So we know that the VPN is OK and that the routing between your remote and local devices through the VPN all is working properly at a basic level and you *should* then be able to get to any other IP address within that same subnet (assuming no other restrictions exist).
But...
You can't get to a POE-powered device (camera) within that same 192.168.x.x subnet from the VPN but can when connected locally from the same device?
Assuming that's correct, do you have any way to power the camera other than the switch? Alternately, do you have another camera/other POE device that you can try? Wondering if there's some restriction that the switch is imposing on the POE port side or maybe by address range. Is your desktop using a DHCP or static address?