I don't have an answer for you, but it is a mystery to me why would anyone still use Quick App, with so many issues and complaints affecting that application.

 

What editing program would you recommend?

 

20 abandoned the quick Desktop GoPro software, maybe another program is better off for a hero 8 and above

 

What editing program would you recommend?

 

The first thing to do is to make sure that the videos are in a format that is supported by Quik. Quik supports a variety of video formats, but it is not compatible with all of them. You can find a list of supported formats on the GoPro website. Also, check the file names of the videos. Quik may not be able to find videos if their file names are too long or contain special characters. However, you can use a video recovery program like Stellar or Recuva.
When importing videos, it is best to use the "Add Media" button in the Quik app. This will allow you to import all of the videos in a folder at once.