Synchronization issues between QuickBooks Online (QBO) and App4S happens when there are connectivity, integration, or configuration problems. I'll provide you with some troubleshooting steps to fix this, Tamex.

First, let's ensure both program have stable internet access as syncing relies on stable and uninterrupted connections. We'll also have to verify that the integration between QBO and App4Sales is correctly set up. I recommend reaching out to their support team to be guided on reviewing your configuration.

However, if everything is working on their end, you can contact our Live Support team, as they have the necessary tools to investigate this issue further. Here’s how:

Please make sure to check their available hours to ensure prompt assistance.

Feel free to revisit this thread if you have additional questions.