Steps to take.
Install this version.
Still no good? Close Videopad, the using Windows Explorer (the file manager) locate this folder and delete all files that it contains...
"C:\Users\<your PC name>\AppData\Roaming\NCH Software\Components"
Reinstall the Videopad version linked above.
If issues persist someone will help if you take a few minutes to share several MOV and mp4 files that fail to load or load without sound. It's not a difficult process.
Upload the file/s to a free server, such as Google Drive or MS OneDrive, get a shared (public) link, copy the link and paste it here or to me in a Private Message via the mail envelope in the top-right corner of this forum. When using Google Drive, if necessary change "restricted" to "anyone with link can view."