Obsolete
http4s uses argonaut-6.2 as of version 0.15. This repo is obsolete.
Why
http4s' main repo has reverted to argonaut-6.1 now that it's supported for scalaz-7.2. But some of the argonaut ecosystem has moved on to the binary incompatible argonaut-6.2. This is for the early adopters.
Dependency
Replace...
"org.http4s" %% "http4s-argonaut" % http4sVersion
... with:
"org.http4s" %% "http4s-argonaut62" % http4sVersion