WiFi networks report the "connected without internet" problem when I turn on the VPN client built into the Firewalla (NordVPN)

Hi everyone, since I configured the Nord VPN account on the Firewalla I have a strange problem, all the WiFi networks connected in cascade to my Firewalla Gold give me the following problem "connected without internet", in this regard, here are the necessary clarifications :

1. My Firewalla is Gold, configured in router mode on which the 3 network segmentations allowed by the device are activated, which then divides the devices into 3 different subnets.

2. the Netgear router that emits the WiFi signal is connected in cascade with the Firewalla in AP (Access Point) mode, and when the VPN client is switched off it works perfectly, when it is switched on the WiFi networks become "without internet".

3. If I try to use the VPN client bypassing the Firewalla (thus activating the VPN connection through the various Nord VPN apps installed on the individual devices to be connected) everything continues to work safely, so the problem lies in the client pre-installed in the Firewalla .

4. At the beginning I had activated the VPN connection for all devices by selecting all the various subnets present in my Firewalla, but seeing the problem I thought that perhaps there were too many devices covered by the VPN (from the official NordVPN app you can connect max 5 devices at a time, so I thought there were too many devices driving the Firewalla's built-in VPN client crazy), so I unchecked all of them and only selected one, but the problem keeps popping up.

5. The problem occurs only with the two WiFi networks (2.4 Ghz and 5 Ghz), the devices connected with wired connection (Ethernet), do not encounter any connection problems.

6. In addition to the Netgear router that I connected in cascade to the Firewalla, configured as AP (Access Point) I also (obviously) have the ISP network modem from which my operator's internet connection arrives, on which the Firewalla is connected.
The WiFi of my ISP network modem has no problem, it continues to work quietly even if I activate the Firewalla's integrated VPN network, further confirmation of the fact that it depends exclusively on the VPN client integrated in the Firewalla.

I am waiting for your feedback also because I have subscribed to NordVPN precisely because I had read that this was fully supported by Firewalla, but for now I cannot use it, so I hope for a quick resolution of the problem on your part.

Greetings