Many issues can be solved by syncing your data between QBO and Boostlingo.
To sync your data, navigate to Configuration → Company → Integrations in your Boostlingo portal. Then click the highlighted link.
Most other errors can be resolved by searching the issue in the QuickBooks Help Center and implementing the solution. Then, re-sync your data as shown above.
If you continue to run into issues, please send a screenshot of your error to support@boostlingo.com.