Try loading both the shape and image from setup() with everything else in draw(). For example:
void setup() {
size(1000, 1000, P3D);
obj = loadShape("dalle_2.obj");
txtr = loadImage("grid3.jpg");
}
Personally, I would do away with the objAbstractShape() function and I’m not sure you really need pushMatrix() and popMatrix() unless there is more to your project than is being shown.