Hey there @jun1119!
The online account management is such an awesome way of staying on top of everything associated with your services. I definitely understand being concerned when you cannot access it.
We have had similar reports, and I would like to take a closer look at what is going on when you try to log in. I will be sending you a private message to your Forum’s Inbox. This way together we can find out what is going on and get it fixed.
I look forward to speaking with you!
Fiona, AT&T Community Specialist