To find the equation of a plane given three points, the user struggles to arrive at the correct equation, which is 2x + y + 7z = -3. The main issue identified is an incorrect calculation of the cross-product, which is essential for determining the normal vector of the plane. Specifically, the user miscalculated components related to the i and k unit vectors. Clarification on these calculations is requested to identify the exact error. Understanding the correct method for calculating the cross-product is crucial for solving the problem accurately.