create_shared_link_with_settings works once, then returns nothing

I can't help with the third party library itself, but can you clarify what you mean you say it "stops"? The Dropbox API itself should always return a response, whether that's a successful result, or an error. You should check how you can retrieve an error result from the library.

For example, if you're calling for the same path multiple times, the issue is likely that /2/sharing/create_shared_link_with_settings returns a shared_link_already_exists error when there's already a shared link for that file/folder.

You should check how to catch that using that library, and then instead call /2/sharing/list_shared_links using direct_only=true to retrieve the existing shared link.