create_block_blob returns ResourceNotFound

[BenG-x]

I experience a problem when trying to create a block blob with create_block_blob with a client using a SAS token to authenticate:

client = Azure::Storage::Blob::BlobService.create(
  storage_account_name: 'my_account_name',
  storage_sas_token: 'sas_token'
)
client.create_block_blob('some_container_name', 'test123.csv', 'some_content')

# Azure::Core::Http::HTTPError: ResourceNotFound (404): The specified resource does not exist.

The credentials are valid and I am able to create a block blob using the Azure Storage Explorer.

I don't get the ResourceNotFound error - I am just trying to create the blob so of course is does not exist yet - according to the README there is also not something I have to do before (like initializing the blob).
Or am I doing something wrong with authentication by SAS token?