Jekyll Assets - link to stylesheet

What is the preferred method for linking to updated stylesheets in Assets 3? In previous versions I know you could use { css style }, but it appears this has been deprecated. Although I am using one of the default configurations - so no changes to config - it does not appear to be working properly.

I wonder if something changed when @envygeeks took over the maintenance and forked it for Jekyll 3. A testing repo - on a previous version of v3 - appears to work correctly using the Minima theme as an example.

Locally, my main stylesheet is in /assets/css with imports coming from _sass. Currently getting a 404 where the link url is appended to the page permalink.

Update

I have resolved the link issue so that it works correctly. However, digests are not showing up.

I have the following configuration:

assets:
 compress:
   css: true
   js: false

 autowrite: true
 cache: .asset-cache
 cache_type: filesystem
 skip_baseurl_with_cdn: false
 skip_prefix_with_cdn: false
 prefix: "/assets"
 digest: true

 sources:
   - _assets/css

 features:
   liquid: false
   integrity: false
   automatic_img_size: true
   automatic_img_alt : true