I'd be glad to help sync your Expensify with QuickBooks Online.
Syncing your Expensify application is done through the Apps menu in your QBO account.
Let me guide you through on how to accomplish this:
Log in to your QBO account.
Go to the Apps menu, then select Find Apps.
Search Expensify, then click on it.
Click Get App now.
By following the steps above, you'll be able to connect your application.
If you need assistance about mapping your accounts, I suggest reaching out to your third-party app support. By doing so, they'll be able to help you with specific instructions on how to properly handle them.
Let me know if there's anything else you need with connecting your Expensify and I'll get back to you.