For the Dropbox (with password) connection method, we choose Dropbox API.

Then, for the shared link on how to get it, you can refer below for more detail. 

To connect with your Dropbox file that is protected by a password, you will need the shared link and the link password.

This is how to retrieve the link password or change the password. If the file is provided by a supplier or dropshipper, please request the password from them.

You will also need to request for the shared link. This is the step to get the shared link. 
Simply click on Share > Copy Link and paste in Stock Sync respective field.

Please make sure the link is correct and it is not the link of the file and not the folder