Diagnosing a Post-Redesign Drop in Interaction Rate

A web app redesigns its dashboard in a minimalist "flat" style, removing all button shadows, borders, and background fills — buttons are now just text in the brand color, sitting directly on a white background, identical in style to non-interactive labels elsewhere on the page. Post-launch analytics show a meaningful drop in clicks on the primary "Export Report" action, even though the button's position and label text didn't change.

1. Using the affordance/signifier distinction, explain the most likely cause of the click drop.
2. Propose two different fixes, at different levels of visual commitment, and the tradeoff between them.
3. How would you validate which fix actually solves the problem before rolling it out broadly?