To resolve the "error communicating with server" issue on your FreeStyle Libre 3, follow these step-by-step solutions:

1. Check Server Status: Before attempting any troubleshooting, verify the FreeStyle Libre server status to ensure there are no ongoing outages or maintenance. You can check the server status here: FreeStyle Libre Server Status - [learn more].

2. Disable Wi-Fi: Turn off Wi-Fi on your iPhone. Sometimes, the app has difficulty connecting through Wi-Fi. After disabling Wi-Fi, attempt to reconnect using your mobile data. This can often resolve connection issues with the server - learn more.

3. Ensure Mobile Data is Enabled: Make sure that mobile data is enabled for the FreeStyle Libre app. Go to your iPhone's Settings, select "Cellular," and scroll down to verify that the app is toggled on to use mobile data.

4. Restart the App: Close the FreeStyle Libre 3 app completely and reopen it. This can refresh the app’s connection to the server.

5. Reboot Your iPhone: Restart your iPhone. A fresh boot can often resolve various software glitches.

6. Reinstall the App: Since you mentioned deleting the app, ensure that you have downloaded the latest version of the FreeStyle Libre app from the App Store and reinstall it. After reinstalling, log in again and see if you experience the same error.

7. Consult Abbott Support: If the issue persists after trying the above steps, consider reaching out to Abbott’s customer support for further assistance. They can provide specialized help and troubleshooting for persistent issues - learn more.

Following these steps should help you resolve the server communication error. If you continue to experience problems, further investigation on potential app-specific issues or server outages may be necessary.