Trying to export files from folders and subfolders to Nakala

A "path/not_found" Dropbox API error indicates that the API call failed because there was nothing currently found at the specified path in the connected account under the relevant root. For example, this can happen if there's a mistake or typo in the path value the app supplies, if the file/folder has been renamed, moved, or deleted from that path, if the app is not connected to the correct account for that particular path, etc.

When specifying the path, make sure you provide the full and accurate path for the desired file under the relevant root. For example, if you have a file named "example.csv" inside a folder named "folder", the path would be "/folder/example.csv". You can find more information on path formats here.

I see Здравко already helpfully covered some of this, but to elaborate a bit, here are several things you can check in particular to debug this:
 

• Make sure you're using a currently accurate path value: You can use files_list_folder and files_list_folder_continue to list the contents of a folder so you can check what the correct path values would be for items in those folder(s). To list the root, set path to the empty string "" when calling files_list_folder. You can use the path_lower or id values returned for the files/folders in that folder to interact with those files/folders.
   
• Make sure you're connected to the correct account for the path value you're using: You can use users_get_current_account to check which account the app is connected to.

• Make sure you're using app folder-relative paths, if your app is registered for the "app folder" access type: Apps with the "app folder" access type can only access the contents of the special app folder that gets automatically created for it. If your app has the "app folder" access type, then it will only be able to access files in the app folder, and the root for any path value supplied by that app will automatically be the app folder root. You can find more information on app permissions here. For example, If your app has the app folder access type and you're trying to access something you can see on the Dropbox web site at "/Apps/<app folder name>/folder/example.csv", you should only send the path value as "/folder/example.csv". Alternatively, if your app is registered for the "app folder" access type but you need to access contents outside the app folder, you'll need to use a different app registration with the full Dropbox access type instead (or you can move the contents into the app folder).

• Make sure you're accessing the relevant root: When using an app with the "full Dropbox" access type, API calls default to the member folder, but if you're trying to access the "team space" (only applicable to members of a team with the "team space" configuration), you'll need to configure that as the root explicitly, as covered in the Team Files Guide.

Given the existence of "Applications" in your screenshot though, it seems like you may have registered an app with the app folder access type, but are trying to access a folder "/Sète" outside the app folder, which would fail, so take note of the third list item above in particular.