Thanks for posting in the Community, Sarah_T88!

Appreciate you checking the default accounts in your Payroll Chart of Accounts, and making sure you've set a primary account on them. The set-up of your payroll chart of account determines where the payroll journals will be posted after exporting to QuickBooks.

If you have done and checked the set up of your payroll chart of accounts through Payroll Settings > Chart of Accounts > Default Accounts. And the exclamation or prompt still showed, I would recommend contacting our Customer Care Team. They might need to check your payroll connection and reset them to refresh the connection. 

You can check this link to learn more about: Set up and configure payroll chart of accounts.

Drop by again if you have concerns about your QuickBooks Online account. I'll be right here to answer them for you.