Looks like the path should be from the perspective of the account you’re sharing from based on the code.
So to share the file blah.txt located in the folder /folder1 from within the admin account (which you’re connecting as), the path to use would be /folder1/blah.txt.
Tip: You can reverse engineer how the Web UI client does shares by using your browser inspector Network tab to look at the request/response payloads (if you’re ever looking for an additional way to cross-reference things).