Network selection is the process by which a phone chooses which mobile network to connect to, either automatically or manually from a list of available carriers. It happens every time your phone loses signal, restarts or lands in a new country.
In automatic mode, which is the default, the phone scans for available networks and picks one based on the SIM’s preferred-network list and signal strength. For travellers this normally just works: you land, take your phone off flight mode, and within a minute or two it finds a partner network and comes online. Many travel eSIMs can use more than one network in the same country, and in automatic mode the phone settles on whichever suitable network it finds first.
Manual selection is the troubleshooting tool. In your settings under mobile or cellular networks you can turn automatic selection off, wait for the phone to list every network it can hear, and pick one yourself. This helps in two situations: when the phone has latched onto a network your plan does not support, and when it clings to a weak signal despite a stronger supported network being available nearby.
The common confusion is that seeing a network in the list does not mean your plan can use it. Manually selecting an unsupported carrier can show signal bars while giving you no data at all, which looks like a broken eSIM but is really just a wrong choice. If a manual pick fails, switch back to automatic, toggle flight mode and let the phone sort itself out. Incorrect APN settings can produce a similar bars-but-no-data symptom, so check both. Whether any network is available at all is a separate question of network coverage.
Concrete example: you land in Istanbul and your phone sits on No Service. Manually selecting a network your plan supports brings the connection up in seconds.
For step-by-step fixes see our eSIM troubleshooting guide, and for the full setup process, how to install and activate an eSIM.