Apple’s iOS 26 update brought a range of improvements to iPhone, but it has also introduced a frustrating problem for some users: iMessage activation failures linked to SIM conflicts. Instead of activating seamlessly, some iPhone owners are finding that their phone numbers cannot be properly registered with iMessage, leading to missed or undelivered messages.
According to Apple’s support documentation, the issue usually occurs when an inactive SIM card is still tied to the same phone number as the active SIM. This is especially common for users who previously used dual SIM configurations or switched carriers but left an old SIM installed on the device. When iOS 26 detects both an active and inactive SIM linked to the same number, iMessage activation may fail or behave inconsistently.
The result is a range of messaging problems that can be confusing for users. Messages may fail with a “Not Delivered” alert, or they may only send as SMS or RCS messages instead of iMessages, showing up as green bubbles rather than the expected blue ones. In some cases, outgoing messages may default to an email address instead of the user’s phone number. Another common symptom is seeing the same number appear twice under Settings > Apps > Messages > Send & Receive.
Apple notes that these issues are not due to carrier outages but rather to the way iOS 26 handles SIM recognition during iMessage activation. For users who rely heavily on iMessage, especially those who have upgraded from older devices or migrated SIMs, the disruption can feel significant.
Fortunately, Apple has provided a clear set of instructions for resolving the conflict. The key step is to remove the inactive SIM from the iPhone, ensuring that only the active SIM tied to the correct phone number remains.
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If the inactive SIM is physical, users should eject and remove it from the SIM tray.
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If the inactive SIM is an eSIM, it can be deleted directly through the Settings app under Cellular or Mobile Service.
Once the inactive SIM has been removed, the next step is to re-enable iMessage. This can be done by navigating to Settings > Messages > Send & Receive and making sure that the correct phone number is selected. In most cases, iMessage will then re-activate using the proper configuration.
For users who still encounter problems after removing the inactive SIM, Apple recommends following its standard troubleshooting steps for iMessage and FaceTime activation. This may include ensuring that the device has a stable Wi-Fi or cellular data connection, verifying that carrier settings are up to date, and checking for any account-related restrictions with the carrier. In rare cases, signing out of the Apple ID and signing back in can also reset the activation process.
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