Verified by Visa - ABSA Problem

Eventually got it working but I still do not know what the problem was.

I contacted ISP and they could not find any problem on their side. Reset router multiple times but the problem persisted.

I connected my phone to my PC for internet access and payment worked. So no problem with my PC settings.

Then changed router to backup router and payment worked. So the problem must be with my ASUS Router I thought.

But when I reconnected my ASUS router it also worked again. How is this possible? Anybody got any ideas about what the problem was?
This is an old post, but will post this in case it helps anyone else.
We have been struggling with this for the past 2 weeks while trying to do testing and we eventually tried incognito mode on Chrome and it worked! We still not to sure why incognito mode would work though?