Q: I'm trying to add this iPad to an existing AT&T account. I try to type in pass code, then go to the SSN & it deletes the pass code I just typed. What am I doing wrong

You are trying to do what?   Do you have an AT&T SIM card ?   Did you buy the AT&T version of the iPad?

Is your iPad cellular or wifi only?

And where exactly are you trying to enter this information?

The iPad cellular account is different from your cell phone account.

 Cheers, Tom

I have the same issue. 

For those that that have responded to your question and don't know, you can now add your iPad to your existing AT&T data plan if you have the shared family data plan.  It's cheaper since it's only $10/month to add the device to share your data plan vice paying somthing like $30/month for 3GB (or whatever level you need).

I was told by an AT&T employee that there are several ways to accomplish this.

1. Call AT&T

2. Do it online at ATT.com (I tried this but their website is down for maintenance)

3. Do it on the iPad (which is what you and I are trying to do).

I have no idea why after entering the passcode and then trying to enter the last 4 of your SSN that the passcode disappears.  Or conversely, if you enter the last 4 of your SSN, then go to the passcode field, that the SSN disappears.  So when you try to continue you get the please enter valid data message.  Seems like a bug in the system.

lizdance - On the iPad in Settings, if you go to "Cellular Data", then click on "View Account" you have 3 options to choose from:

1 - Set Up New Account

2 - Add to Existing AT&T Account

3 - Transfer Service From Another iPad

This of course is if you have not already setup a payment or plan previously.

If you have then you can cancel your current plan, then when you go back into View Account you wil be presented with the 3 new options.

Texas - They can be separate or you can tie it into an existing AT&T plan if you have a shared data plan.