Please make sure that you have Read/Write access of the Destination where you are putting the files.
Destination panel should be expanded.
Or try to Add (Choose Add from the file handling option as highlighted in the picture below) a File from desktop to Lightroom catalog to see if it works(this will allow us to confirm whether the issue is when you Copy files)
Thank-you Akash Sharma for your panel and explanation. Their was another reason that the files were not loading. I was not following the proper file folder path in selecting the destination file folder.
Your panel provided me with that insight. It's been a frustrating last few months arriving at that solution. But along the way I gained a lot of knowledge in how to handle any future problems.
Sent from my iPad
Glad to know it helped.
Thanks for the update.