Problem
Your QuickBooks file was corrupted and you created a new one, but your business units are still mapped to the old file, making them unavailable to connect in the new file.
Solution
Business units cannot be mapped to multiple QuickBooks files. Remove the business units from the old QuickBooks file before deactivating it and the re-map them to the new QuickBooks file.
Make sure you have ServiceTitan Web Connector and QuickBooks Desktop open.
On the navigation bar, go to Settings > QuickBooks Desktop.
Click on the old QuickBooks file that is causing the issue.
Remove the business units from the old file.
Click Deactivate.
Go to the new QuickBooks file.
On the Business Units Assigned row, click Edit.
Map the business units to the new file.