Where is my Guest Network UI tab? Facebook???

[Geedsen]

The last few days we had weird problems with our Wifi, our Wifi has two network SSID's and hey exist for years already, with the same password.
But the last few days our mobile phones and laptops were not able to connect to the guest network. "Incorrect password" or unable to get an IP address.
So I checked the routers and what I see is weird, the UI page for the Guest Network only shows me a "Facebook Wifi" page.

And it does this on several routers (4 with orinigal Asus firmware) . They all still are broadcasting the original guest network, but I can no longer get to that page....

And on two routers I have Asus-Merlin, and when I go there I see another problem,
The menu on the left side no longer appears...

What is going on?

 

[Ripshod]

Update the firmware (if possible), reset the router(s), and start again from scratch.
In your images the router's are in AP mode - there are no guest network settings in AP mode. What about your settings on the main router?

 

[Geedsen]

Update the firmware (if possible), reset the router(s), and start again from scratch.
In your images the router's are in AP mode - there are no guest network settings in AP mode. What about your settings on the main router?

Firmware update was done on several routers, problem remained.. And also in AP mode there is a Guest Network.
But I figured it out. Somehow the problem is with the lastest version of Microsoft Edge, it shows a diffent page for Guest Network than Chrome or DuckDuckGo. I tried clearing cache but that does not seem to help.

 

[Tech9]

And also in AP mode there is a Guest Network.

This Guest Network in AP Mode is more like extra SSID. It has no separation from the main network.