Hello suzi66. Welcome to the forums.
I have moved your post out of that other thread, since your problems don't seem to be related to double layer discs.
It sounds like your dvd player does not have the capability to play mpeg 4 video, which isn't all that unusual.
You may have to convert your video clips to dvd-video format before burning them to a disc. This is usually fairly easy using a free tool called AVStoDVD.
Download the program, install it and make sure to set it to make dvd video that fits your area. In the US and Canada we use NTSC format dvds. In most of the rest of the world they use PAL specifications.
The installer will ask if you want to set it to NTSC or PAL, so that is easy to do. Also, you want to set it to use the HC encoder with 2 passes. This is one of the options while installing, so again, not hard.
Once it is in your computer, start the program, then click on the green + sign to import your mpeg4 file into the program. Do this for each clip you want to import.
If you want a menu to select individual clips, just click on the DVD Menu button at the top of the screen. You should then click on Run Editor. If the menu is set up the way you want, just close this little pop up window. If you want to change something, put a dot in the Edit circle and make your changes. Then close the pop up window.
That takes you back to the main window. Make sure you know where you are putting this new dvd video on the hard drive. You can change the Output folder if you wish.
Click the Start button to begin encoding.
Once it is done, you can burn to a disc, and it should play on your dvd player with no issues.