Issues like QuickBooks Error 15215 arise during QuickBooks payroll update or installation. It is always advised by QuickBooks to get these issues fixed only with the help of QuickBooks expert professionals who are surprisingly good at fixing these errors. Any changes made in the QuickBooks software on your own can corrupt your files and cause loss of your data.
If you want to try on your own try a few things mentioned below.
Close QuickBooks Software and Restart your system
Check the firewall and antivirus settings
Install the update manually
Choose to run your system as administrator
If none of the measures help you fix the issue, contact the QuickBooks support team immediately.