Hi Nascardork187,
You cannot combine MP4 format videos, if their codecs, sizes, frame rates, or bit rates are different.
Please try combining other MP4 videos that were taken using the same setting/quality.
For more info, please visit this link:
http://guide.playmemoriesonline.com/help/en/pc/pmh-video-edit.html.
If my post answers your question, please click the "Accept as Solution" button.
Regards,
-Anthony