I get this message:
Could not copy a file to the destination folder because it is not writable.
I don't know what that means. I do not have the box to copy a file to another folder or drive checked.
That message is indicating that the destination folder does not have write permission. Use your system file browser to check that folder and ensure that it has both read and write permission.
I had the same issue and was unable to copy files from my camera. The error message was also about the destination folder not being writable but it turned out that the folder LightRoom was trying to create already existed in the destination.
Once I deleted that folder, everything worked.