The router has connected to the iPad easily but when I load the QU-PAD app my QU-PAC is not showing up!? It D-Link doesn’t appear to be connecting to the router?
The QU-PAC must connect to a wireless router via an ethernet cable plugged into a LAN port on the router. The DIR510L has no such port, so it will not work. Something such as a D-Link DIR-813 AC750 Wi-Fi Router is what you need.
See the QU-PAC manual for how to set up the mixer IP address.