Receiving a 9999 error code when trying to link my WF business checking account to my quickbooks online account

Thank you for reaching out to the Community. It's my priority to help you sort this out, @mark-rodriguez.  

You can manually link your Wells Fargo checking account to the QuickBooks Online. Doing this will help you download the current transactions automatically. It will also, categorize your bank and credit card transactions for you. 

Let me walk you through: 

1. On the left pane click Banking. 
2. Choose Upload transaction manually. 
3. Click browse and upload a transaction from CSV file. 
4. Tap Next. 
5. Drop-down arrow select the Account type, or click the + Add new. 
6. Hit Next.
7. Fill out the field from the pop up message. 
8. Click Save and Close. 
9. Map the CSV columns, tap Next.

Pop up message will appear saying do you want to import now? Click Yes.

Once done, you need to confirm or approve all the transactions showing from the Banking.  

I encourage you to visit this article to learn more about the connecting you bank in QuickBooks: Connect bank and credit card accounts to QuickBooks Online. 

Please let me know if you need further assistance about linking your bank account to the QuickBooks. I'll be here to help you out. Have a great weekend!