RELEASE depends on being able to read repository metadata files, which are not always available or up to date
(Common problem with s3 repos, although I doubt that’s relevant here)
I've never seen a situation where an artifact can't be found by lein,, but manually using another resolver to cache the artifact fixed it - lein is looking for an artifact with a specific tag (RELEASE), and reagent-frontend/lein-template isn't offering anything with that tag
also, why did it only check your local cache, and not search maven or clojars?