Files downloaded from dropbox won't open

I have a folder of mixed Adobe files, Indesign, Illustrator JPEGs, PNGs etc. None of them will open as each application thinks they are already open or locked or says they are not suitable files. The files where on dropbox but are now stored locally. Other files and folders I have do not behave like this. The files have data and varying sizes so I am confidnet they are there and not failed downloads.Any clues welcome? Running Adobe CC and Catalina 10.15.