I've bought an iPhone 4 and the text and calling work fine, as does wifi. However, when trying to use internet without Wifi I get a "Could not activate cellular data network - PDP authentication failure".

How can I fix this?

  • After update to ios 9 this hapens to me. Seems ios9 is too much bug.
    – user148323
    Commented Sep 24, 2015 at 2:03
  • @Yudo The iOS 9.0.1 update notes mention a fix for APN - you might be right about a bug in 9.0
    – bmike
    Commented Sep 24, 2015 at 2:59

9 Answers 9


There have been a lot of different attempts to fix this general error in different ways. Some of these may work for you.

  • Remove the SIM card from iPhone 3G, turn off the phone, reboot, then reinsert the sim card and wait an hour or two.

  • Go to Settings -> General -> Reset -> Reset Network Settings on your phone to reset the network setting on the iPhone.

  • Change SIM Card

  • if nothing else works, call AT&T and have them reset your number.

  • Resetting the network settings fixed it for me... even though nothing changed. Very strange! Commented Nov 11, 2010 at 21:05

I just got this problem fixed for Argentina calling t-mobile tech support. They were great.

Calling worked. SMS worked. Data - did not work. APN Authentication Failure

Tried before this - airplane mode - cell settings reset - power cycle (turn off/on) phone - hard reset - network setting reset - several APN profiles (only useful if you change to local SIM card)

The data roaming ON was set on my phone, but that wasn't working on movistar service. They had me dial a special code to turn that on on the network for my line.


And it turned data roaming on and instantly - data was back on.



You might also try going into Settings > Carrier and choosing manual carrier selection - bizarrely enough, that worked for me. See https://apple.stackexchange.com/a/52624/12164


Try to hard -reset the whole phone using the power and the home button.

  • This is so counter-productive I have to downvote it.
    – user13716
    Commented Sep 16, 2015 at 0:46

Airplane mode off/on,then off,,manual search network ,enable network by a tik sign, date time ,year most up-to-date, get sim card loaded off,switch off 10minutes,put the SIM card ,switch on phone.its done on iPhone 4. Or try the settings sent OTH (over the air) by network operators directly to your phone for a GPRS/edge data transfer protocol connectivity. Such problems occur when you get a hardware change which do not carry the same apple part number and do not authenticate . Sometimes you may try using a logic card from another i phone 4/4s phone to try rectify the same issue. Such was the case when a touch/display screen was replaced with another available in the gray market.

  • 2
    I am having a very hard time following this. Consider revising so your answer is clear and concise. For more info see How to Answer in our Help Section
    – Allan
    Commented Jul 14, 2016 at 11:19

Bro just call your Internet service provider. They will help you with it. I had same problem but after found that my validity of Sim was over and I need to recharge. Call your carrier and just talk to them.


You may try download and install APN configuration file and install again. This solution worked for me


holding both buttons (power and home buttons) at the same time seemed to work for me :)


in most cases this error occores due to insufficient credit in you mobile connection. please pay your bill to the service provider and try again. it should work.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .