HP EliteBook 840 G11 will not connect to Wi-Fi or keeps disconnecting

The checks in more detail

A work network that needs a certificate or a login will refuse a laptop whose certificate has expired, and only the IT team can renew it. For a home or public network, forget the network under Settings, Network and internet, Wi-Fi, Manage known networks, and join again with the password. Toggle Airplane mode and restart. Check whether the fault is the laptop or the network by connecting a phone to the same Wi-Fi and trying the laptop on a phone hotspot. If the hotspot works, the router or the access point is the issue.

If it fails everywhere, open Device Manager and look at the Wi-Fi adapter under Network adapters; a yellow mark means a driver problem, which HP Support Assistant or HP Image Assistant can fix with the right driver. In the adapter's properties, on the Power Management tab, untick the option that allows the computer to turn it off to save power, which causes drops after sleep. In the power plan, set the wireless adapter to Maximum performance. Run the Windows network troubleshooter, then reset the network from Settings, Network and internet, Advanced network settings, Network reset;

on a managed laptop ask IT first, because this removes saved profiles and VPN settings. Update the BIOS and the Wi-Fi driver. Check that a VPN or security agent is not blocking traffic: turn it off briefly as a test if policy allows. Keep the laptop within a good range of the router, and prefer the 5 GHz or 6 GHz band. If the adapter disappears from Device Manager, restart, and then contact HP or IT, since the card may need replacing under warranty.