add land line to my existing accounts online

Try entering the landline account number instead of the phone number. Here are instructions on how to link accounts: https://www.att.com/support/article/wireless/KM1008925/

Tried that several (24) times as well.  Still says "something is wrong, try again"

Thanks

We just signed up with Att June and how about over 20 hours;a manager at the Leland NC store says he ported our number; now we are willing to get new number and same manager sent us home Friday saying it will be on in 3-4 hours. Nothing. A package? Coming? Telling us to do it... THANK YOU AND PLEASE HELP US BOTH..

Please open your own topic as your post has nothing to do with the OP's issue. Explain better what your issue is. Also since you went to an AT&T store I'm assuming this is a cell phone issue, if that's correct open your topic in the wireless forum. 

Hello Barandar, let's get you pointed in the right direction for support for your wireless service. 

As the ace stated, let's create a new thread in our wireless forums. We are ready to help.

Thank you For visiting AT&T Community Forums!

Carlton, AT&T Community Specialist 

I am having the same issue. I was told by the customer service rep that my zip code is wrong with the billing department and as a result when I try to add my landline to my existing account it throws that error. I have opened two tickets in the last month to get the zip code fixed but still no joy.

What same issue? Did you try the solution posted? If you aren't getting satisfaction by working with customer service, you can escalate to a customer care executive by filling out the forum, ignore the header. 

Spoom2, the issue with not being able to add my landline account to my existing att login. Spent another hour on the phone with customer service to be told it's not my zip code, the website is broken. Apparently it's been broken for a month which is why the solution posted doesn't work. I can't register my landline account. I can't add it to my existing account. I can't even pay my phone bill online using the pay without signing in option. I find it ludicrous that this is a known problem and customers are forced to call in to and deal with the abysmal ATT call center. 

Did you read the post directly above yours?