Samsung One UI 9 Update: Fix SIM and Mobile Data Issues

If you searched for “Samsung One UI 9 update SIM not detected mobile data not working,” start here: a missing SIM and a working SIM without internet need different checks. Don’t jump straight to a factory reset. First, establish whether your phone sees the line at all.

Is this a confirmed One UI 9 bug?

Samsung announced the wider One UI 9 rollout on September 16, 2026. However, that announcement does not establish a universal SIM failure. An issue appearing after an update is a useful clue, not proof of its cause. The checks here follow Samsung’s connectivity guidance; they are not a confirmed One UI 9-specific patch.

Before changing anything, note your Galaxy model, carrier and exact software build. Look under Settings → About phone → Software information. Also record whether you installed a beta or a regular update. Menu labels can vary by model, region and carrier.

Match your symptom before changing settings

Restart and check the selected SIM

First, restart your Galaxy through the power menu. Then open Settings → Connections → SIM manager. Check that your physical SIM or eSIM appears and is switched on. With two lines installed, make sure you are checking the intended one.

Next, select the correct line for mobile data. Some variants show a preferred or primary SIM rather than separate controls. Don’t assume the line used for calls is also the line providing internet. Finally, confirm that Mobile data is enabled in Quick settings.

• Check whether the carrier name appears.
• Try loading a webpage with Wi-Fi off.
• Test an ordinary call separately, if your plan supports calls.
• Write down whether one line fails or both lines fail.

These observations make the next step more precise. For example, working calls with failed browsing point you toward data settings rather than immediately toward a SIM replacement.

If your Galaxy says “SIM not detected”

Open Settings → About phone → Status information → SIM card status, where available. Check whether a network appears. Samsung’s SIM detection troubleshooting guide covers recognition checks, reinserting a physical card and diagnostics.

For a physical SIM, power off the phone before removing the tray. Use the correct tray hole, not a microphone opening. Check the card and tray for damage. If necessary, gently wipe the contacts with a soft, dry cloth, then reseat the card according to your model’s tray layout. Never force it.

If possible, test your SIM in another compatible, unlocked phone. Alternatively, try a known-working, compatible SIM in your Galaxy. A failed cross-test is evidence to share with support, not a reason to keep changing APNs.

For an eSIM, skip the tray steps. Instead, ask the carrier to verify activation if the profile is missing or unavailable.

If the SIM works but mobile data does not

Check your plan and data controls

First, confirm in your carrier account that the line is active and has data available. Then inspect Settings → Connections → Data usage for a data limit that may have stopped access. Also check for a carrier outage before repeatedly resetting the phone.

When testing, distinguish “nothing loads” from “one app fails.” If only one app is affected, broaden the diagnosis beyond the SIM. Our mobile data troubleshooting guide can help you continue without treating every app problem as an update failure.

Check the APN without guessing values

The Access Point Name, or APN, connects your carrier’s mobile network to internet access. Open Settings → Connections → Mobile networks → Access Point Names. Compare the selected profile with your carrier’s official instructions.

For a standard carrier line, the menu may offer Reset to default. Before using it, save any provider-supplied custom settings. Travel eSIMs may need their own APN, so follow the provider’s instructions instead of copying settings from an unrelated network.

If APN controls are unavailable, ask your carrier what is supported. Don’t install an unknown configuration profile or use random APN values from a forum.

Check travel eSIM activation and roaming

If your regular SIM works but a travel eSIM does not, focus on that profile. Confirm its destination coverage, activation conditions and remaining allowance. Then verify that it is selected for data. Follow the provider’s roaming instructions for that line, rather than enabling roaming indiscriminately.

Our guide explains how to switch on data roaming on Samsung. Check your home carrier’s charges before changing its roaming settings.

Considering a replacement travel eSIM? Check your exact Galaxy variant’s compatibility first. A different plan is not a guaranteed fix for a phone-wide connectivity problem.

Reset mobile network settings, not the whole phone

If earlier checks fail, try Settings → General management → Reset → Reset mobile network settings. Read the confirmation screen carefully. Samsung distinguishes mobile resets from Wi-Fi and Bluetooth resets on supported software; other versions may group network settings together.

A mobile network reset restores the cellular configuration. Custom APN settings may need to be entered again, so keep the provider’s instructions handy. This is not the same operation as a factory data reset. Samsung’s Galaxy data usage guidance explains the reset and APN precaution.

Next, reconnect and test the same webpage again. Also check Settings → Software update for an official update over Wi-Fi. Don’t assume an available update specifically fixes your issue unless its release notes say so.

Know when to contact your carrier or Samsung

Contact the carrier first for activation, provisioning, account restrictions, outages or replacement SIM questions. If a known-working compatible SIM also fails in your Galaxy, ask Samsung about device diagnostics. Samsung Members offers SIM diagnostics on supported devices.

For a suspected update regression, submit a Samsung Members error report. Include your build number, carrier, symptom, time of failure and the checks you completed. Attach screenshots and system logs if you consent. Keep personal identifiers out of public posts.

Make the report specific: “Calls work, browsing fails on this line with Wi-Fi off” is more useful than “the update broke everything.”

FAQ