MP4 files recovered but not playing

[Charlieb1981]

I recently deleted a shortcut folder in error- and so deleted the content of the main folder. all files are videos in MP4 format.

Recuva has found and restored them all, but now they wont play- I get the same message for them all- shown below:

' This file isn’t playable. That might be because the file type is unsupported, the file extension is incorrect, or the file is corrupt.

0xc10100bf ' 

the files were deleted and restored within 48hrs, the desktop is running Win 10, and these files were saved originally on an external hard drive that has plenty of extra space available and hasn't been used in between deletion and recovery.

file sizes all range from very small upto about 3MB

Any help appreciated as to what has caused this and how it can be fixed,