There are steps for QuickBooks maintenance release server not responding- firstly reboot the desktop, another solution is run Quickbooks desktop as the Windows administrator, the third solution is verified use tls 1.0 is checked, and use tls 1.1 and use tls 1.2 are unchecked in the internet options Window of internet explorer, restart windows in selective startup, installing updates manually, etc.
https://mathomatic.org/quickbooks-error-15215/