As has been said there are lots of variables that could cause your issue.
I’ve have never used mix station but going by the QU pad app indeed the firmware of the mixer and the needs to be the build version. The current app version is 1.93 and the current QU mixer version is 1.95.
Check you mixer firmware by going to the home screen menu or the set up menu under the utility tab.
For you WIFI connection are you using a standard router connected directly to the mixer?
Have you ever connected to and controlled the mixer using an iPad with the Allen Heath
QU Pad app?