I have a list that is customized with DFFS. This works fine for me, logged in as a site collection admin.
For another user, the form loads without any DFFS features, other than the “Enhanced by DFFS” menu at the bottom. There are no errors in the dev console or network trace. We’ve tested with both Edge and Chrome.
DFFS is working for the same user on a list in a separate subsite in the same site collection.