Clarifications on the POST request from OpenHab

maybe it’s a trivial question for you, but I would like to clarify this.
I installed a third router on the LAN I use as an access point. My configuration is:
router1 (gateway) provided by the ISP and not configurable.DHCP on for a range of addresses
router2 (AP) used only for wifi devices (UPNP and DHCP off)
router3 (AP) used only for wifi devices (UPNP on and DHCP off)

From OH I send a request: {http = “> [ON: POST: http: //xx.xx.xx.xx: xx /? On_3]”, autoupdate = “false”} I use to switch on one device in another home

If UPNP on router3 is off OH does not send the request, while from the browser it works, unlike if on everything works, also from OH.

I state that before the installation of the router3 everything worked, and the router2 has always had UPNP and DHCP turned off

thanks for the answers