Free Adobe video conversion wmv to mp4 works but cannot download video and audio - only audio

I was pleased to see a free Adobe video conversion program wmv to mp4 and it seems to have worked really well. Unfortunately, the download option in the conversion program only sends a freeze frame of the first frame and the audio (which is fine). I opened Adobe Express which gives editing options and it plays perfectly there also BUT I cannot download the working verions and get the same result just a frozen first frame and good audio playing.

I'm not an expert so an easy to understand explanation would be appreciated.

Can anyone help? Thanks