HA in DMZ - HomeKit stopped working

Hey folks,

today I finally did the big security step I wanted to do for so long - I segregated my network into two LANs (with two firewalls within two available consumer routers). But now I notice that my HomeKit isn‘t working anymore… all devices are not available and I can not pair a new HomeKit device (= homebridge) in the Home app.

I have the following setup:

Internet
— Router1 (with Firewall1), 192.168.1.1
—— DMZ with all IoT devices including HA
—— Router2 (with Firewall2), 192.168.1.254 in network of Router1, 192.168.2.1 as gateway in its own network
——— Private LAN

I can’t setup my homebridge when I’m in my private LAN.

How can I reanimate my homebridge / HomeKit with the DMZ setup? Everything else is working properly…

Update: It doesn’t neither work when I’m via VPN in the same network as the HA (192.168.1.x).