When the File Copy Service (FCS) isn't working properly, QuickBooks Error 15243 happens during payroll or software updates. QuickBooks is unable to finish the updating process because of this problem. To fix it, you must enable the FCS, check the status of your payroll subscription, and properly update QuickBooks to guarantee seamless operation and prevent service interruptions. For professional QuickBooks advice and assistance, call 1.855.738.2784.