Both the README and the troubleshooting page contain this outdated advice:

Note: The middleware placement is sensitive. If the middleware before silk.middleware.SilkyMiddleware returns from process_request then SilkyMiddleware will never get the chance to execute. Therefore you must ensure that any middleware placed before never returns anything from process_request. See the django docs for more information on this.

That "django docs" link hasn't gone to the right point in the Django middleware page since Django 1.9, which - as far as I can tell - is the last version that had process_request(). I eventually worked this out after having been scared by this note into trying to work out what it meant before placing the middleware.

I'd do a PR with improved advice, but I'm new enough to Silk that I don't know what it would be.