Seeing that "Not registered on network" message on your Sony Xperia 1 VI is incredibly frustrating. It means your calls, texts, and mobile data are all dead in the water. This usually happens when there's a hiccup in the communication between your phone and your carrier's network. Before you assume the worst, start with the simplest fix. A force restart can clear out temporary software glitches that block the connection.
Press and hold the Power button and the Volume Up button together for about 10 seconds. Keep holding until you feel the phone vibrate and the Sony logo appears on the screen. This is a deeper reset than a normal restart and often resolves one-off network registration failures.
Toggle Airplane Mode to Force a Reconnection
If a restart didn't do the trick, try forcing your phone's cellular radio to reconnect from scratch. Swipe down from the top of your screen to open the Quick Settings panel and tap the Airplane Mode icon. Wait for about 15 seconds to let all wireless radios fully deactivate, then tap the icon again to turn it off.
Your Xperia will then search for and attempt to register on the strongest available network. This process is a quick and easy way to re-establish that initial handshake with the cell tower without a full reboot.
Check and Reseat Your SIM Card
A SIM card that's come slightly loose in its tray is a surprisingly common culprit. Power your Xperia 1 VI off completely. Use the SIM eject tool (or a small paperclip) to pop open the SIM tray on the side of the phone.
Carefully remove the SIM card, give both the card's gold contacts and the inside of the tray a gentle wipe with a soft, dry cloth, and then firmly reseat it. Push the tray all the way back in until it clicks, power the phone on, and give it a minute to find the network.
Verify Your Carrier Account Status
Sometimes the issue isn't with your phone at all. If your prepaid balance has run out, your postpaid bill is overdue, or there's an account provisioning error on your carrier's end, your phone will be blocked from the network. I'd recommend checking this before diving into more technical fixes.
Try logging into your carrier's website or app from a Wi-Fi connection, or give their customer service a call from another phone. Confirming your line is active and in good standing can save you a lot of unnecessary troubleshooting.
Reset Your Xperia's Network Settings
Corrupted network configuration files can prevent a successful registration. Resetting these settings will wipe all your saved Wi-Fi networks, Bluetooth pairings, and cellular preferences, forcing your phone to start fresh.
To do this, go to Settings > System > Reset options. Tap on Reset Wi-Fi, mobile & Bluetooth and confirm. Your phone will reboot. After it starts back up, you'll need to reconnect to Wi-Fi and your Bluetooth devices, but this often clears the path for your cellular connection to work properly.
Manually Select Your Network Operator
Your phone might be trying to automatically connect to a network that's having temporary issues. You can manually force it to register on your home carrier. Head to Settings > Network & internet > Mobile network > Carrier.
Turn off the "Choose automatically" toggle. Your phone will search for available networks. When the list appears, select your carrier's name from it. This direct approach can bypass automatic selection problems.
Update Your Phone's Software
Software updates frequently include patches for connectivity bugs and improvements to modem stability. Given that Sony's update schedule can be less frequent than some competitors, it's important to install them when they arrive.
Go to Settings > System > System update and tap "Check for update." If an update is available, download and install it over a stable Wi-Fi connection. A software refresh can resolve network issues that appeared out of nowhere.
Clear the Phone Services App Cache
Android uses a system app to manage the phone's connection to the cellular network. A corrupted cache in this app can lead to registration failures. Navigate to Settings > Apps > See all apps.
Tap the three-dot menu in the top right and select "Show system." Find and tap on "Phone Services." Go to Storage & cache and tap "Clear cache." This doesn't delete any personal data, it just removes temporary files that might be causing trouble.
Test With a Different SIM Card
At this point, it's time to rule out a faulty SIM card. If you can, borrow a known-working SIM card from a friend or family member (on a different carrier is fine for this test) and insert it into your Xperia 1 VI.
If the borrowed SIM card registers on a network without any issues, then your original SIM is likely damaged or deactivated. You'll need to contact your carrier for a replacement. If the new SIM also fails, the problem is isolated to your phone.
Perform a Factory Reset
This is your last resort software fix. A factory reset will erase all data, apps, and settings from your phone, returning it to its out-of-the-box state. It eliminates any deep-seated software corruption.
Back up everything important first. Then, go to Settings > System > Reset options > Erase all data (factory reset). Follow the prompts to confirm. After the reset is complete, set up the phone as new without restoring a backup immediately, and see if it can register on the network. If the error persists after a clean factory reset, the issue is almost certainly hardware-related.