I am brand new to SketchUp, but I have used AutoCAD for around 25 years. I am a retired carpenter, so I have studied 100’s of plans.
I started by drawing a simple isometric view of my deck on my home with the idea of a remodel, I don’t know what I did but the vanishing point shifted to the front of the drawing. The vertical posts in the rear of the drawing appear longer than the same length posts in the front. This is a very confusing perspective. It started out OK then I must have done something wrong.
Could you upload the SKP file so we can see what you did?
Perhaps it’s something simple like you switched the camera to Parallel Projection (Camera menu) and need to set it back to Perspective. When you’re used to looking at a perspective view, Parallel Projection can create the illusion of the vanishing point being in front.