For those of you getting the "We Couldn't Verify Your Business" error message, AA chat directed me to login using my
personal login at
https://aadvantagebusiness.aa.com/app/login.
Worked perfectly, and sent me directly to the business page (with transfer to personal option).
I believe this is the solution for those who signed up for the Aadvantage CitiBusiness Platinum Select but registered with their own Aadvantage number.