As @Hans Z mentions above, the issue is the hex notation is not the actual value that must be encoded, it is an already encoded as hex. So when you try to encode with base64 it fails.

The following CyberChef link breaks down how to the value of the CLI command chain you linked above actually works

https://gchq.github.io/CyberChef/#recipe=SHA2('256',64,160)From_Hex('Auto')To_Base64('A-Za-z0-9%2B/%3D')&input=NWZDaFlpMnZIdVZnMkh4dFAyeXNNdnhqY3pyejFXb2tLV0RON3ExZ095ag&oeol=NEL