Network/Data Issues after UI 9 update

Hello @phoenix9826,
I understand how unexpected and frustrating it is to have your mobile data stop responding completely right after a system update, especially when you depend on your device throughout the day.
Since you have already performed extensive network troubleshooting, please try these additional steps to see if they help restore your connection:

Boot into Safe Mode: Turn off your device, then press and hold the Power button until the logo appears. As soon as it does, press and hold the Volume Down button until the phone finishes restarting. You can review the official Samsung Support Safe Mode Guide for precise visual steps. Check if your data works in this state to see if a third-party app is conflicting with the new software.

Contact Your Carrier: Sometimes a major OS update requires a provisioning update or a new eSIM/physical SIM profile activation from your network provider.

Perform a Factory Data Reset: If all else fails, returning the phone to its default state can clear out deep software conflicts caused by the update. *Please ensure your data is backed up completely before proceeding, as this permanently erases everything*. Navigate to Settings > General management > Reset > Factory data reset. Review the details, tap Reset, enter your security PIN or password, and select Delete all. For reference and more detailed steps you can check out the official guide here.

Give these addiotional steps a try and let us know the results so we can assist you further if needed! 

For my S25, after oneui 9 updated, mobile data keeps getting disconnected after turning on, the data icon keeps flickering on and off, then I go to Settings > Connections > Mobile networks, and turn off VoLTE. Now everything is back to normal. Hope it can help.

Estou com o mesmo problema. Já tentei de tudo e nada resolve.