I had OSX with Java 1.6 installed, and I just installed jenv along with Java 1.7:
$ jenv local \'1.7\'
$ jenv versions
  s         
        You need to install the jenv maven plugin, try the following command and reload your shell:
jenv enable-plugin maven
I had a similar problem. I got things running by prefixing all command with jenv exec:
jenv exec mvn -version
Now, there's a new option how to set JAVA_HOME via jenv export plugin:
jenv enable-plugin export
See https://github.com/gcuisinier/jenv/issues/44#issuecomment-233124185