When QuickBooks Point of Sale (POS) is not connecting to the server, it affects sales processing, inventory tracking, and financial data updates. Common causes include network connection problems, firewall or antivirus settings blocking POS access, incorrect hosting configurations, or issues with QuickBooks POS services not running. Ensuring the network connection is stable, configuring the firewall to allow POS access, verifying hosting settings, and restarting necessary POS services can often resolve these issues. Proper server configuration and addressing data file location or corruption problems are also essential steps in troubleshooting.