Right now there is an issue with qbo and online banking.  Intuit needs to fix it:  https://www.artesanibookkeeping.com/error-9999-quickbooks-online/

Resolution for 'business online issue: 'i cant sign into citibank business online' available: Yes.

The business online issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the business online issue yourself by looking for a resolution described in the article. If it is a complex business online issue or you are unable to solve the issue, you may contact us by clicking here or by using other business online support options.

For more information about resolving issues related to business online in Quickbooks/QBO or to get support for the issue 'i cant sign into citibank business online', click the link below: