Cannot manage apple ID due to "unknown error"

My macbook (latest Yosemite) popped up a prompt for my iMessage password and then would not accept multiple attempts at the same correct password. I thought it might be 2-step verification related (couldn't remember if I needed an app-specific password), so I attempted to log in to my Apple ID and couldn't.

I attempted the steps outlined here and didn't help (delete cache/cookies):

Apple ID two-step verification - unknown error

My steps:

1. Got a pop-up on my MacBook (latest Yosemite) asking for my iMessage password, and it would not accept my regular appleID password
2. Went to manage my appleID and see if I needed a new app-specific password (I DO have 2-step verification on)
3. Logged-in, asked for me to verify through 2-step
4. Got the confirmation code just fine on my phone (initially, phone had not taken latest 8.2 update, so I updated the phone and ran through the whole thing again to exactly the same steps)
5. Entered the code and bounced back to appleID homepage with the message "an unknown error occurred"