The captive portal is not always reachable from all devices. Many of them works properly and only some connect to the wifi ssid but are not redirected to the Cambium captive portal.
Is it a device issues or its network card? How could I solve it?
Are you using some external captive portal, onboard AP portal or cnMaestro Guest Portal? Try to load the captive portal in a laptop Google chrome browser and looks for any component load failure or any errors seen in the browser debug console window. (Open Chrome DevTools | Chrome for Developers). Check things in the Network and Console tabs in the debug window of the browser. If you are able to narrow it down to specific devices which are having problem then we can go to next steps to see what could be the problem. A DNS latency, DHCP IP latency, slow network, etc and can lead to such issues apart from some real problem on the splash page itself.
This should work, does the other working device in same location connected on same AP works fine? Do you know the details of such device like make and model, OS version, etc? Apple devices sometimes might not auto pop up the portal, this is sometimes due to issues in the apple iphone itself sometimes. What kind of devices always found to be working at same location when this given device didn’t work?
ok If I understand correctly then some windows laptop don’t auto pop up the captive portal window till you try to browse something. I believe this is a windows specific issue which is not triggering the captive portal detection module. Ideally it should trigger the captive portal detect HTTP GET request on each WiFi connect but I have seen this doesn’t work well on many windows devices and upon reconnect like post session timeout, etc it might not display the captive portal page at all or randomly it might show up sometime. Apple devices are more notorious on session timeout behavior. I don’t think anyone can do about it apart from Microsoft itself.