This can happen when there was a network issue during the startup of the Supervisor.
Manually update the Supervisor, in case there is an update pending. This can be done from the Updates panel.
This can also be done with the CLI, by running the following command:
ha supervisor update
In case this doesn’t work. Check the logs, if there’s an error where a host can’t be resolved (eg: lookup ghcr.io: no such host) there might be a problem with your network settings (eg: dns server that can’t be reached).