It may be a folder permission issue. Where is the folder located? It it a local drive? If the drive is external then please create a new folder on the desktop and put the source images in that folder. Then see if it works.
A couple of other things it could be.
1. It may be a folder permission issue. In Finder, right click on the folder and select get info. If all 3 user permissions are not set to read/write then set all of them to read/write and try again
2. It could be a corrupted folder permission token. Those are stored internally by Adobe. The only way I have seen to fix that is to create a new folder with a different name. So again, creating a new folder on the desktop and trying would test for this too.
- This reply was modified 1 year, 7 months ago by Pixnub.