Home Assistant needs to know when it has a stable network connection in order to disable functionality which requires that. Without this check you will face an increased number of errors and performance issues due to connection timeouts.
From the host shell, first execute the following:
busctl get-property org.freedesktop.NetworkManager /org/freedesktop/NetworkManager org.freedesktop.NetworkManager ConnectivityCheckAvailable
You just need to re-enable connectivity checks by executing this command:
busctl set-property org.freedesktop.NetworkManager /org/freedesktop/NetworkManager org.freedesktop.NetworkManager ConnectivityCheckEnabled b true
It may take a bit for the message to go away as all checks are scheduled on timers. You can force it to recheck immediately by executing the following commands:
ha host reload ha resolution healthcheck
You need to set the connectivity uri in Network Manager’s config. You can do this by adding the following to
[connectivity] uri=http://checkonline.home-assistant.io/online.txt interval=600
Afterwards you will need to restart NetworkManager by either rebooting the host or executing this command:
systemctl restart NetworkManager
As mentioned above, the checks are on timers so the message may not go away immediately unless you force an immediate re-check. If you continue to see the message after a while or after forcing a re-check then start over at the top of this solution. You may need to separately enable the check now that it is available.