This is usually due to lack of write permission on the destination fold.
How did I change that? I wish I could call someone!
There are plenty of "help" resources right here in the LR forum, but this might help:
You may not have changed the destination folder permissions. It may have always been "read only or you're selecting the wrong folder in the Import Destination path. It helps us to help you if you provide information about your system OS,etc.