Error message "Could not start DNS service on <ip-address> port 53 UDP (Socket error 10049 The requested address is not valid in its context)"

This is probably because you have previously configured Simple DNS Plus to listen for DNS requests on an IP address which is no longer present on the computer.

To fix this, go to the Options dialog / DNS / Inbound Requests section, and select which IP addresses Simple DNS Plus should listen on, and then click the OK button: