Looking at the build file of that plugin:
version := "0.1.2"
the correct version seems to be "0.1.2"
, not "0.12"
. (see here).
Furthermore, you have a typo in the arifact name: It's "ensime-sbt-cmd"
not "ensime-sbtt-cmd"
.
Normally, sbt should find stuff in oss.sonatype.org even if it doesn't get through to Maven Central. However, I'm not sure this goes for plugins as well, therefore you might try to explicitly add a resolver for it:
resolvers +=
"Sonatype releases" at "https://oss.sonatype.org/content/repositories/releases"