I'm using smart groups with access controls so that when I add contacts to a particular group they get access to some contacts. I have two identically configured wordpress users with two identically configured contacts records, but one user sees the correct list of contacts, and the other user only sees himself. Any idea what I might have misconfigured?
Before trying anything else, clear your caches. Find it under Administer menu » System Settings » Cleanup Caches and Update Paths.
After that, make sure you're setting both the user roles AND the ACLs correctly - but assuming you've done that, the best advice is at https://shouldiblamecaching.com.