Authentication problem on paths with user_id

I have the Admin API working, including authentication, but it fails when I have a user_id in the path.

I can successfully POST to /admin/v1/users to create an account, but when I try to POST to /admin/v1/users/{$user_id} I get an invalid signature error. Same when I try DELETE to ``/admin/v1/users/{$user_id}` — with no URL params. So the issue definitely appears to be the path in the signature when it includes a user id.

My authentication formula is the same for the calls that work — with no user id — and the ones with user id that don’t work. Any guidance on what the issue might be here?

Just FYI in case anyone finds this — I was lowercasing the path, so when it included the user id it changed the value of the user id to all lowercase.