QuickBooks Error 6190 and 816 occur when the company file is not accessible due to a mismatch between the transaction log file and the company file or when another user is in single-user mode. To fix this, ensure all users are logged out of QuickBooks. Use the QuickBooks File Doctor tool to identify and repair file issues. Switch to multi-user mode after resolving any discrepancies. Regular backups can prevent data loss.

For professional assistance, contact QB Data Service at +1-888-538-1314. Our experts are here to ensure your QuickBooks runs smoothly and efficiently.