What to do if the "PDP Authentication Failed" error occurs?

This error is a network configuration issue. Resolution steps:

1. Check if the APN settings are correct.
2. Switch the network mode (e.g., from 5G to 4G).
3. Reset the device's network settings (iOS: [Settings] - [General] - [Transfer or Reset iPhone] - [Reset] - [Reset Network Settings]; Android: [Settings] - [System] - [Reset] - [Reset Network Settings]).
4. Reinstall the eSIM or reinsert the physical SIM card.