Being connected to Wi-Fi does not always mean the network has granted internet access. Hotels, libraries and guest networks may require a separate sign-in or terms page. Firefox can detect this and open a captive-portal tab.

Confirm whose network you joined

Check the Wi-Fi name against information from the venue or its staff. Inspect the sign-in page’s address and what it requests. A browser notification that a login is needed is not proof that an unfamiliar page deserves your email password, payment information or other private details.

If the portal does not appear, try opening an ordinary website or reconnecting to the intended network. Save active work before disconnecting. If the same problem affects another device, tell the network operator; repeated browser resets are unlikely to repair a venue-wide access problem.

Keep network policy in view

A VPN or proxy can interact with the network’s admission step. On a managed work computer, follow your organisation’s instructions for guest networks instead of disabling protection on your own. Ask the provider or administrator for its supported portal procedure if the sign-in cannot be reached.

After completing a legitimate portal step, open a familiar HTTPS site and confirm that ordinary browsing works. Return to the intended protected work connection before accessing sensitive business systems. If a warning persists despite working internet, record when it appears and ask the network operator about its detection or redirect behaviour.

A captive-portal message can also occur on a wired or home network. In that setting, note whether all devices are affected and whether the router or provider is requesting setup. Treat that as a network investigation, not automatic evidence that Firefox needs reinstalling.

Source: Mozilla Support.