ABSA app not working on WIFI

I spoke to someone working at ABSA because i was having trouble with the double factor authentication with the ABSA app. I was told the app only works on mobile data and not WIFI(they had no idea why). That seems very stupid. I've been stranded several times not being able to do payments when outside the country or out off data. The app doesn't tell you you need to use Mobile data not WIFI. This is just bad design and very inconvenient.