Welcome to the Community, @Gilmanbl. I want to make sure you're able to connect your Citibank credit card account in QuickBooks Online (QBO).
To give you an idea, the connection window that is displayed is not generated or controlled by QBO but by CitiBank.
Also, a possible cause for this button to being greyed out might be a hold on the account that does not allow the connection to QBO. Or the user who is attempting to connect account may not have access or permission to add a bank.
I suggest you verify the status of your account with your bank and also check the user's access who is attempting to connect your bank or credit card account in QBO.
For future reference, read through this article: Manually upload transactions into QuickBooks Online. It helps you learn about importing your bank transactions into QuickBooks.
Get back here if you have any other questions about connecting your bank to QuickBooks Online. I'll be glad to help you more.