When you’re run ffmpeg command and receive an error message similar to the following:
| Unsafe file name '00 M00S.mp4' mylist.txt: Operation not permitted | 
This is because there is space in target filename in the text file. To fix this issue, add
| -safe 0 | 
before
| -i | 
If you have this issue from Combine MP4 files using FFMPEG on Windows (without re-encoding), simply replace command in step 7 to the following:
| ffmpeg -f concat -safe 0 -i mylist.txt -c copy output.mp4 | 


Thank you, worked for me