One issue I had getting my Pi3b with official 7" display and Hifiberry DAC+ running was setting up Wifi.
What eventually solved my issue was to connect the Pi to my router then use a browser at http://runeaudio to set up my wifi and save my profile. For some reason rune wouldn't allow me to save the settings on the Pi interface but worked perfectly from a browser.
Hope this helps somebody because I tried all sorts of workarounds to no avail until I tried the above.