After considerable frustration trying to connect my Santander banking app on my phone, with wifi connection to my 2927ax, I discovered that turning off "Block IP packet from WAN with inconsistent source IP addresses" enabled me to connect.

Oh nice one!

I had the same trouble with another popular banking App, which worked with mobile data active but not via a Vigor Router (2862) using wifi, although it started working all of a sudden some months later... ...I can now see that I turned that exact setting off - for something else - and didn't put two-and-two together, thanks!