Hi @Martin although we have had quite a few issues with NewDay over time, we are not aware of a general issue here.
The determination of whether the bank’s app or website is opened when we pass over to them is made by the bank/card provider rather than Snoop. However, sometimes on Android the device’s settings can impact this. We have a particular issue with Samsung devices for example based on how their default browser and ‘app to app’ link handling is setup.
That said, in this example I don’t believe that’s the problem. The screenshots show you are successfully logging on to NewDay’s service and for whatever reason they are showing that error message. This I’m afraid is not something we can directly diagnose or resolve as we have no sight on what is happening when you are logged into the bank’s app or web service.
My assumption would be that your card account has some sort of setting that is preventing external access - this can sometimes be a temporary thing caused by a new card being issued, extra security checks that might have been added or even something like a transaction that has triggered some extra fraud checks. I’m afraid this will need a contact to their customer support team to ask them to investigate. Please don’t let them tell you the problem will be with Snoop as that can’t be the case here (frontline staff often just assume it must be us without understanding how Open Banking works! 
).
If you don’t get anywhere, please can you contact us through the app and I’ll contact their Open Banking support team.
Paul