Render don't start in blender while using Cycles

I just appended two blender files to get my two models in one scene. when I hit Render Image. It doesn't start rendering although before appending the two files the render was working properly. I tried to render the default scene(Cube scene) in blender and it rendered. I guess the problem is not with my camera because I created a new camera and made it my active camera and still not working. all the objects appear in the viewport shading and none of them are hidden. one more thing the GPU compute option is no longer active besides it was active before and worked with me.

I just figured out the problem. the sequencer in the output properties was checked on. to check it off go to Output Properties > Post Processing > Sequencer.