QuickBooks error 1603 generally occurs when there has been an issue in the update process of the QB software and the update installer might have encountered internal damage. The resolution for this issue can be achieved when you reinstall the QBDT extension file in the windows after uninstalling...
quickbooks customer care
quickbooks customer care number
quickbooks customer service
quickbooks customer service number
quickbooks customer supportquickbooks customer support number
quickbooks tech supportquickbooks tech support number
quickbookstechnicalsupportquickbookstechnicalsupport number