Movie Maker files won't play on WMP or VLC or Naver Media

I have old videos recorded while on vacations the last 10 years. Most with a Sony CamCorder. Many are video clips of the same place or thing. So I used Windows Movie Maker to combine like subject matter in to a single movie. The original files are MPEG files, and they save as MP4 files. The originals play fine on WMP, VLC, and Naver Media Player. However, the combined files will not play. I used Freemake to convert the new MP4 files to .mpg and they still won't play. In all instances I only get the audio.

I'd appreciate any suggestions about what I can do to combine these short clips, and still be able to play them on the PC.

Thank you.

Why not join them directly with Freemake?

I didn't know I could do that, or how..? A little direction, please?

At the right side of the buttons Video.....Paste URL, under the logo freemake.com you will see a switch: Join files.
Joining is coupled with a conversion; only joining does not seem possible.

I saw that button, however its not live. I can't toggle it on or off.

Check first the videofiles in the main window. Then, toggling should work.

An alternative might be Handbrake (free). See for merging: Batch-Convert Or Merge An Entire Folder Of Videos With HandBrake