RBK13 Several Connection Issues

Hello,

I have an Orbi RBK13 (https://www.netgear.com/orbi/rbk13.aspx) and I'm experience a few strange issues, but I can't find how to sort this out. 

Simptoms:

- The Orbi has the latest Firmware installed (v2.3.6.18);

- Connected over a ethernet cable to the router O2 HomeBox 6741 (https://www.manualslib.com/manual/1488434/O2-Homebox-6741.html)

- Over the app, on the upper right corner it always says "Offline" as in the screenshot attached. But it's not offline:

- All apps on my phone and tablet can access the internet over the Orbi connection. My Smart-TV also has no issues with the connection;

- My Amazon TV Stick is not able to connect to it, and always says that there is no internet connection;

- On different laptops and also tablets using different browsers, I can make a search on Google. But if I click a link, I see a page asking for username and password (screenshot also attached) with /BRS_wanlan_conflict.html in the end of it. This also happens if I type an address on the browser directly.

Any idea?