I have integrated Wallee to my shopify account. I have also input all the BS Payone information into Wallee.
However when I click Wallee on Shopify apps it doesn't show anything - it only shows a blank page.
This is normal, so a blank page is expected, as it is only for connection and not for login.
Please go to wallee directly to log in. It is not possible from the backend of Shopify.