To fix Error 6123, ensure QuickBooks is updated, rename the .ND and .TLG files, use the QuickBooks File Doctor, move the company file to a different location, or restore a backup. Disable antivirus/firewall temporarily if they block QuickBooks. Reboot in Safe Mode if issues persist. link: https://medium.com/@joshua31weissman/learn-effective-ways-to-resolve-quickbooks-error-6123-5641a9c127be