If your OnePlus Open is showing "No SIM card" or "SIM card not detected," you can't make calls or use mobile data. This is a common problem with foldable phones, and it's usually something you can fix yourself in a few minutes.
I'd start with the simplest fix first. Press and hold the Power button for about 10 seconds until you feel the phone vibrate and the screen goes black. Keep holding until you see the OnePlus logo appear. This force restart clears temporary glitches that can mess with the SIM reader.
Check the SIM Card and Tray
Since the OnePlus Open is a foldable, the SIM tray is on the side of the device. Power the phone off completely before you do anything. Use the included SIM ejector tool to pop out the tray.
Take a close look at the SIM card's gold contacts. Look for any scratches, dirt, or discoloration. Gently wipe the contacts with a clean, dry microfiber cloth. While you're at it, check inside the SIM tray slot on the phone for any dust or debris.
When you reinsert the tray, make sure the SIM card is seated correctly and the tray slides in smoothly. A misaligned card is a common reason it won't be read. If you have another phone handy, test your SIM card in it to rule out a faulty card.
Toggle Airplane Mode and Verify SIM Status
Swipe down from the top of your screen to open the Quick Settings panel. Tap the Airplane mode icon to turn it on, wait about 10 seconds, then tap it again to turn it off. This resets the phone's radio connections.
Next, open your Settings and go to Mobile network. Make sure the toggle for your SIM card is switched on. Sometimes after an update or a restart, a SIM can get disabled in software even though it's physically present.
Update Your Software
Software bugs in OxygenOS can sometimes cause connectivity issues. Go to Settings > About device > OxygenOS version. Tap on "Check for update."
If an update is available, download and install it. Your phone will restart. It's a good idea to plug it into the included 67W SUPERVOOC charger during this process to make sure it doesn't run out of battery.
Reset Your Network Settings
This will clear all your saved Wi-Fi networks, Bluetooth pairings, and mobile network configurations. It won't delete your personal files like photos or messages.
To do this, go to Settings > Additional settings > Back up and reset > Reset phone. Then, select Reset Wi-Fi, mobile & Bluetooth. Confirm the reset and your phone will reboot.
After the reset, you'll need to reconnect to Wi-Fi and re-pair Bluetooth devices, but it often resolves persistent SIM detection problems.
Configure Your APN Settings
Incorrect Access Point Name (APN) settings can prevent your SIM from connecting to your carrier's network properly. Go to Settings > Mobile network > select your SIM > Access Point Names.
Tap the three-dot menu in the top right and select "Reset to default." If that doesn't work, you may need to enter the APN details manually. You can get the correct settings from your carrier's website or by contacting their support.
Try Manual Network Selection
Your phone usually finds the best network automatically. If that's failing, you can try choosing it yourself. Go to Settings > Mobile network > Network operators.
Turn off "Select automatically." Your phone will search for available networks. When the list appears, select your carrier's name. This can sometimes force a connection when the automatic process is stuck.
Clear the SIM Toolkit Cache
System apps that manage the SIM can accumulate corrupted cache data. Go to Settings > Apps > App management. Tap the three-dot menu and select "Show system apps."
Scroll down and find "SIM Toolkit." Tap on it, then go to Storage usage. Tap "Clear cache." This doesn't delete any important data, just temporary files that might be causing trouble.
Consider a Factory Reset
This is a last resort for software-related issues. Before you begin, make absolutely sure you have a recent backup of everything important. Go to Settings > Additional settings > Back up and reset > Reset phone.
Select Erase all data (factory reset). Follow the prompts to confirm. Your phone will wipe itself and reboot to the initial setup screen. You can then restore your data from the backup you made.
Check for Physical or Antenna Issues
If you've tried everything and the SIM still isn't detected, there might be a hardware problem. The internal SIM card reader could be damaged, or there could be an issue with the antenna connections.
Given the OnePlus Open's folding design, internal ribbon cables related to connectivity run through the hinge. While not common, a fault there could cause this symptom. At this point, contacting OnePlus support for a diagnostic would be the next step.
