Thanks for bringing this concern to our attention. I can provide information about the error 999 you're getting when connecting your bank.
You can now report this online banking error straight to our product engineers. They have tools that may help you with getting around this issue.
Click the Report Issue when receiving the error message.
Enter information being asked, such as name and email address.
You will receive an email directly from the team that resolves banking errors, not from QuickBooks Online Customer Care. Please note that most issues are resolved within 8-10 business days but it can take up to 21 business days.
Please know that we value your patience while dealing with this concern. Let me know how things go after following the troubleshooting steps provided in the email. I'll be on the lookout for your reply and to further assisting you if you have other questions. Wishing you and your business continued success.