Sometimes, before or after installing major updates, a QuickBooks error may appear. QuickBooks Error 15215 may appear while a user is downloading payroll updates. The error message says that QuickBooks is not able to verify the digital signature. When there is a conflict with a background application when a user attempts to download payroll updates, QuickBooks Update Error 15215 may occur. The background application may be using excessive bandwidth, thus inhibiting QB Desktop Payroll from accessing the server. QuickBooks Payroll may not be able to connect to the server because your firewall is not properly configured.