I am trying to navigate the spreadsheet sync feature in Excel, but an error appears: "App initialization error: No companies found for this user. Please try again."

Welcome to the Community, Shaira. I'm here to share information so you can navigate the Spreadsheet Sync feature in Excel successfully.

When managing reports in a spreadsheet, please know that only admin users can handle them. Moreover, users added as accountants or firms to a company can no longer run statements, add, edit data, or create budgets.

Since you've already attempted to log in via Excel, you can also access Spreadsheet Sync directly from your QuickBooks Online Advanced dashboard to get rid of the error.
Here's how:

1. Click the Gear icon and select Spreadsheet Sync.
2. On the Home tab, select Spreadsheet Sync from the ribbon.
3. Click Get Started, then Sign in.
4. Type in your QuickBooks user ID and password to access the tool.
5. Search your company from the list if you have multiple companies.

If the issue persists, you can contact the Spreadsheet Sync support immediately. Our team is available Monday until Friday, from 6 AM to 6 PM PT. You can reach out to them by signing into Spreadsheet Sync and selecting 'Help,' and then Contact Us.

You can refer to this article for more details on resolving common errors encountered with Spreadsheet Sync: Spreadsheet Sync troubleshooting.

Furthermore, you can check this guide to learn how to create a spreadsheet report and organize your QuickBooks Online Advanced company: Get started with Spreadsheet Sync for QuickBooks Online Advanced or Accountant.

I'll be here to assist if you have further questions about the Spreadsheet Sync feature. Just let me know in the comments.