Answer first: restart the device, then test each service separately
au states that after eSIM activation, Android phones and iPhones may receive an SMS instructing a restart after line information has been written. The next step is to restart the device.
Do not treat that SMS alone as proof that mobile data, voice, SMS and au Mail/MMS are all working. Those functions should be verified separately.
Keep line switching, eSIM profile setup and service testing separate
au's activation flow varies by contract type. For applicable changes, au instructs users to complete line switching before the eSIM profile setup. After that, restart when instructed and verify services independently.
| Layer | What to confirm |
|---|---|
| Line switching | The contract line has been switched when required |
| eSIM profile | The profile is installed and the au line is enabled |
| Restart | Restart after the line-information message when received |
| Mobile data | Test with Wi-Fi off |
| Voice / SMS | Test independently from mobile data |
| au Mail / MMS | Check app setup and preferred-SIM conditions |
If mobile data does not work after restart
au recommends checking that the au eSIM is enabled. With dual SIM, temporarily turn off the other carrier's SIM and test the au eSIM by itself. Also confirm that the au line is selected for mobile data.
If mobile data works but au Mail or MMS does not
au recommends a device restart first. If the mail/MMS app still does not work, turn Wi-Fi off and try the app over mobile data. This is a different diagnostic layer from basic eSIM activation.
Dual-SIM setup can affect au Mail initialization
For au Mail initial setup, au instructs users to set voice, messaging and mobile data to au, or temporarily disable the non-au SIM. After setup, requirements can vary by device; au lists a specific exception for OPPO smartphones.
Do not delete the second SIM simply to troubleshoot. Temporarily disabling it is enough for the initial isolation test.
Do not delete the eSIM as the first troubleshooting step
If the eSIM is removed, reissue and activation may be required. First restart, confirm the au line is enabled, check the selected data line, isolate the second SIM if present, and then use au's official reissue/activation guidance if the problem remains.
Official sources
- au — eSIM activated but au Mail/MMS is unavailable
- au — mobile data unavailable after eSIM activation
- au — eSIM activation procedure
Procedures vary by contract type, device and dual-SIM configuration. Re-check the matching au procedure before making irreversible changes.
