Creates a new Asset at the given path. If an asset already exists at the given path, its original rendition is updated instead of creating a new asset. If inputStream is null new Asset is created without original rendition. If an asset already exists at given path and inputstream is null, original rendition is not updated.
I think that your Input Stream is null, due to which the original rendition is not getting updated.
Input Stream is the input stream of the new asset's original binary.
You can also achieve the same using Assets HTTP API, as follows: