Why a 3D Secure 2 payment was Authorised with transStatus: A : Attempted to Authenticate from the ARes and without a challenge?

This can be considered as the frictionless flow of native 3D Secure 2, which can be expected when the issuer decides that authentication is unnecessary and proceeds directly with the authorisation. It can be recognized on the Payment Details page of the Customer Area with:

1. 3DS requested - A: Attempted to authenticate;

2. 3DS challenged - No (n/a);

3. Liability shift -  Yes, issuer will bear the financial risk for fraud.

which looks like the image below in the Customer Area: 

In these cases, liability shift applies, as it can be seen above.