Seeing "No Service" or a missing signal icon on your OnePlus Open is a real headache, especially when you need to make a call or use mobile data. This usually means your phone can't connect to your carrier's cellular network. The good news is that most of the time, this is a temporary glitch you can fix yourself.
I'd start with the simplest fix first, which often works. Grab your phone and perform a force restart. Press and hold the power button for about 10 seconds until you feel a vibration and see the OnePlus logo appear on the screen. This clears out any temporary software bugs that might be blocking the cellular radio.
Check Your Basic Connection Settings
It sounds obvious, but it's worth a quick look. Swipe down from the top of your screen to open the Quick Settings panel. Make sure the airplane icon isn't highlighted, as Airplane Mode disables all wireless connections. Also, tap the mobile data icon to ensure it's turned on. Sometimes a recent update or app can toggle these settings without you realizing it.
Next, try toggling your SIM card off and on. Go to Settings > Mobile network. Tap on your SIM card and switch the "Enable" slider off. Wait about 30 seconds, then turn it back on. This forces the phone to re-register with the network, which can kickstart a stalled connection.
Reinsert Your SIM Card
A loose or dirty SIM card is a common culprit for signal problems. You'll need the SIM ejector tool that came in the box. Find the tiny pinhole on the left side of the phone's frame and gently push the tool in to pop out the SIM tray.
Carefully remove the SIM card and take a look at the gold contacts. If you see any dust or debris, gently wipe them with a soft, dry cloth. Blow into the SIM tray slot as well to clear any dust. Reinsert the SIM card, making sure it's seated correctly in the tray, and push the tray back into the phone until it clicks.
Reset Your Network Settings
If the simple stuff didn't work, a network settings reset is a strong next step. This will erase all your saved Wi-Fi networks, Bluetooth pairings, and cellular configurations, but it won't touch your personal photos, messages, or apps.
To do this, open Settings > Additional settings > Backup & reset. Tap on "Reset phone" and then select "Reset Wi-Fi, mobile & Bluetooth." Confirm your choice and enter your lock screen PIN if prompted. Your phone will reboot, and you'll need to reconnect to Wi-Fi and re-pair Bluetooth devices, but it often resolves persistent cellular issues.
Update Your Access Point Name (APN)
Your APN is like the phone's address book for connecting to your specific carrier's internet. If these settings are wrong or outdated, you'll have data and sometimes voice problems. The easiest way to fix this is to reset them to default.
Navigate to Settings > Mobile network > your SIM card > Access Point Names. Tap the three-dot menu in the top right and select "Reset to default." Your phone will load the standard APN for your carrier. After it resets, restart your phone to ensure the new settings take effect properly.
Manually Select Your Network Operator
Your OnePlus Open usually picks the best network automatically, but sometimes it gets stuck trying to connect to a weak tower. You can force it to search again and choose your carrier manually. Go to Settings > Mobile network > your SIM card.
Tap on "Network operators." The phone will search for a moment. When the list appears, you should see your carrier's name (like T-Mobile, Verizon, etc.). Select it from the list. If your carrier isn't listed, there might be a wider service outage in your area.
Check for a Software Update
OnePlus regularly releases OxygenOS updates that include bug fixes for connectivity and other system issues. It's worth checking if you're running the latest version. Go to Settings > About device > OxygenOS version and tap on the icon at the top to check for updates.
If an update is available, connect to a Wi-Fi network and download it. Make sure your phone is charged above 30%, or better yet, plug in the included 67W SUPERVOOC charger. After the update installs and your phone restarts, check if your signal has returned.
Use the Phone Information Menu
Android has a hidden diagnostic menu that lets you interact directly with the cellular radio. Open your phone's dialer and type *#*#4636#*#*. This should open the "Testing" menu. Tap on "Phone information."
On this screen, you'll see a "Run Ping Test" button and a dropdown menu for "Set preferred network type." For most users, selecting "NR/LTE/GSM/WCDMA" is the best option. You can also try tapping "Turn off radio" and then "Turn on radio" to cycle the connection. Exit the menu and restart your phone afterward.
Review Your Installed Apps
Sometimes, a recently installed app can interfere with network services. Think about any new apps you downloaded around the time the signal problem started. If you use a VPN app, try disabling it or even uninstalling it temporarily to see if that's the cause.
You can also boot your OnePlus Open into Safe Mode. This temporarily disables all third-party apps. Press and hold the power button until the power menu appears, then press and hold the "Power off" option on your screen. Tap "OK" when prompted to reboot to Safe Mode. If you have full signal in Safe Mode, a downloaded app is likely the problem.
Contact Your Carrier for Support
If you've tried everything here and still have no service, the issue might be with your carrier account or the SIM card itself. Give your carrier's customer service a call. They can check for outages in your area, verify that your account is in good standing, and ensure your line is properly provisioned for your OnePlus Open.
They might also suggest getting a new SIM card. SIM cards can wear out or become faulty over time. Swapping it for a new one at a carrier store is often a free and quick process that solves mysterious signal issues.
