Would you be able to print out the actual request being sent to Dropbox so I can take a closer look? Be sure to redact the access token though.
In any case though, I notice that you appear to be calling for the path "/Salford-test/Test client", but in your other screenshot you're checking the configuration for a different folder "SALFORD". Make sure you're checking and calling for the right folder, and one that you currently have access to.