Nope, that hasn't fixed it. Sign in page is here:
This page is also attached.
You can try firstname.lastname@example.org with either "Peterpiper1" or "Pumpkin123" as the password, both combinations are registered in our user database table yet the verification still fails.
We have added the Unique Database Value validation type and, ever since, ALL of the Validation Show If regions are displayed BEFORE the form is even submitted.
It's just one thing after another and I've completely lost the will to live with all of this now.
Please can you help us?