I followed the instructions on the webpage exactly as shown, but it shows that the installation was not successful after completion. What is the reason and how can I resolve it?
ffmpeg 8 is not supported in 14.3 (it will be in 15). I would recommend removing that from the path, and in a new WL session evaluating $VideoEncoders. This should pop up a dialog that will offer to install a supported version of ffmpeg, and the only necessary action will be clicking the install button and restarting the kernel.