Flex200 V5.42(ABUI.1) crashed this morning: after reset is back online but no WiFi clients

GiuseppeR

Hello everyone,

this morning a USG FLEX 200 with latest V5.42(ABUI.1) onboard crashed and it was unable to come back online with its entire network (7x Zyxel appliances):

As you can see it crashed multiple times:

I was just able to see it online but not the rest of the network (switches, APs, servers and so on…) because the firewall was unable to serve the DHCP server. It was able only to reboot itself via Nebula. Nothing else.

As you can see the offline issue was for the entire network:

So I had to go on site.

I tried to plug in a WAN2 to check if it was something related to the ISP connection, but the firewall was unable to get the WAN2 also when unplugging WAN1.

So I had to reset it.

After I reset it, it went online automatically (I set nothing, neither the ISP connection parameters and that is strange…) letting the rest of the network go online so the customer was able to work again.

The problem is that I cannot see the exact list of devices, linked to it, for example it does not show anything on WiFi while I'm sure that there are devices that goes wireless there (e.g. printers, a pair of tablets…):

As you can see here:

I have a PC too that is linked to that site WiFi, but zero devices on Nebula.

How can I understand what happened?

Someone else saw a similar behaviour?

GiuseppeR

EDIT.

After almost half a day I start seeing again WiFi devices in my list:

Please compare this to my previous screenshot 😎

Zyxel_Melen

Hi @GiuseppeR

The device offline timestamp seems match the Nebula incident period.

Nebula Cloud Service Incident 2026-06-15 09:52 - 17:53 (UTC+0) — Zyxel Community

About the wireless client counts, I'm checking on it.

GiuseppeR

Hi @Zyxel_Melen

I understand the fact that this issue seems to match the Incident period, but it is strange that the firewall took down the entire network: it was unable to release a dynamic IP also for my laptop when I went on site (the reason why I had to reset the firewall).

The reality was that the client was NOT able to go online until I went there.

When there is a Nebula Incident the difference is that you cannot reach Nebula services, but I was able to see that specific ORG down and on site they were unable to go outbound.