Network Error when attempting to fetch resource.

[Johns52]

I have been using Media Converter and Muxer - Audio Tools in Firefox for many years and it has worked very well, but today I was trying to use the Video and Audio Combiner, to add an audio m4a file to an mp4 video and it wont work, gives an error "Network Error when attempting to fetch resource" As I said I have used this Video and Audio Combiner, many times and it worked well. can anyone tell me how to fix this error. Thanks John This is what shows at the bottom of the screen 1:53:44 pmSelect a tab then drag one or multiple media files into the designated box. All the media files will be downloaded to the directory that is set in the settings tab (default directory is your Desktop directory). 1:55:49 pmSaving a temp file in C:\Users\John\AppData\Local\Temp\260_The Beatles - Girl (Pic's) ADD audio as not Beatles.mp4 1:55:49 pmSaving a temp file in C:\Users\John\AppData\Local\Temp\853_Girl .m4a 1:55:50 pmNetworkError when attempting to fetch resource.