WAN iface ignores DHCP OFFERs?!

[nerd]

Euhm..

Was trying to get IPv6 working on my new OPNsense install.
Moved the server running OPNsense to my lab, reconnected it and now OPNsense seems to ignore any and all DHCP (IPv4) OFFERs coming in from the ISP. OFFERS seem to get lost somewhere between host and client.
Switch port-mirror sees the OFFERs but a packet capture from OPNsense WAN interface doesn't. Mmm.

Running this on Proxmox host. I don't need any special config for the interfaces right?
Any ideas on how to troubleshoot this further?

sigh.. why does the solution always appears shortly after I've made an idiot of myself on a public forum?
I just wasted several hours because
solution: I had  a 802.1Q tagged public vlan on the Proxmox host but an untagged/native vlan on the switch. :-[