Hi Michal,

Byron here from the Customer.io technical support team.

Without knowing more about how you have the SDK configured and other app details, it’s tough to say exactly why iOS devices are not synced to your profiles.

If you haven’t had a chance to review our troubleshooting guides, I recommend starting there. We have a bit of info regarding device sync between staging and production builds, if that is relevant to your situation: https://customer.io/docs/sdk/react-native/updates-and-troubleshooting/troubleshooting/#why-arent-devices-added-to-people-in-production-builds

If you haven’t already tried updating the SDK to the latest version, I recommend that step  in case we have already resolved an issue related to device syncing: https://github.com/customerio/customerio-reactnative/releases/tag/3.1.13.

Once updated, try enabling debug logging in the app and then try to sync the device to a profile to check for errors in the logs: https://customer.io/docs/sdk/react-native/updates-and-troubleshooting/troubleshooting/#capture-logs

If you continue you see the issue, would you mind writing submitting a support ticket for the issue?