If your iPhone or iPad is saying PDP Authentication Failure when you try to access the Internet please follow the steps below.
- Put your device into airplane mode for a few seconds.
- Turn off the phone and reboot.
- If you are still getting the PDP Authentication Failure Message, go to Settings > General > Reset > Reset Network Settings. This will reset the networks setting on the iPhone or iPad.
PDP (Packet Data Protocol) is the networking used by your device to connect it to thru the carriers to the public internet. Any error in authentication means your device has not received the the appropriate settings needed to automatically connect. Assuming no issues with the validity of the carrier service, any PDP Authentication Error could indicate corrupted, mismatched or missing networking information.
Doing a fresh network reset, on a strong data connection should allow the network settings to be updated properly.